UK metric timeline

UKMA has attempted to produce a timeline showing events that led to the UK’s current muddle of measurement units and to its failure to fully adopt the simple, rational, coherent and universal alternative – the metric system. We have concentrated on events in the British Isles. Readers who wish to see the wider picture – the metric system has been truly international for over 145 years – may wish to consult additional sources. In particular, a comprehensive timeline covering world events, not just those involving the UK, may be found at:


AD 32 – 412
Britain is occupied by the Romans and adopts Roman measures. These are common throughout much of Western Europe, the Balkans, Romania, the Middle East and North Africa, and include the Roman pound and mile (the latter being ‘mille passus’ or 1000 passus – one passus is two paces of a Roman legionary).

412 – 1066
Anglo-Saxon and Danish England.
New measures such as the furlong appear alongside those of the Romans.

Aethelstan becomes the first King of a united English kingdom.

The first recorded law on weights and measures in England states that, “Only one weight and one measure shall pass throughout the King’s dominions.”

1066 onwards
The Normans retain English measures, but introduce continental measures such as the ounce.

Magna Carta says “Let there be one measure …” However, enforcement in medieval times is often left to chance, and this clause in Magna Carta should be seen as an indication of a problem but not foreshadowing a solution.

1400 onwards
A ‘rough and ready’ decimal system is used increasingly for navigation at sea:
100 fathoms = 1 cable
10 cables = 1 nautical mile (approximately one minute of arc of latitude along a meridian)
1 knot = 1 nautical mile/hour

Edmund Gunter, an English mathematician, introduces one of the earliest decimal measuring devices: a chain comprising one hundred links with a total length of one tenth of a furlong (22 yards). His aim is the simplify the measurement and calculation of the area of land. The words ‘chain’ and ‘link’ thereby acquire additional meanings.

Galileo is tried by the Inquisition. The trial puts a stop to the scientific tradition in the Mediterranean. The scientific revolution moves to Northern Europe.

1642 – 1659
There is civil war, revolution and a republic in England.
John Wilkins, born in Oxford and a student and graduate of the University, becomes Warden of Wadham College in 1648. He is joined by a number of experimental scientists, including Robert Boyle and Robert Hooke, who during the 1650s make Wadham one of the leading scientific institutions of Europe.

Restoration of the Monarchy. Wilkins loses his posts at Oxford.
In November, twelve experimental scientists, some from the Oxford ‘college’ and including Boyle, Isaac Newton and Wilkins meet in London to hear a lecture by Christopher Wren. Wilkins chairs the meeting, which agrees to form a scientific society with him as secretary.

King Charles II becomes patron of the society which is renamed The Royal Society. Hooke is appointed curator of experiments.

Wilkins, now Dean of Ripon and FRS, publishes a theory of everything entitled “An essay towards a real character and a philosophical language”. It is likely that many of his ideas were formulated during discussions with colleagues at Oxford and London. They include proposals for a new simplified measurement system with key features that will be incorporated in the metric system over a century later:
* a universal standard of length,
* a simple relationship between length and volume (or capacity),
* a simple relationship between length and weight or mass,
* units increasing by a factor of 10.

Newton becomes President of The Royal Society, and sets about undermining the reputation of rivals, in particular Hooke. Wilkins’ work is largely forgotten.

The Kingdom of Great Britain is formed by the Act of Union of England (and Wales) and Scotland. The Act achieves uniformity of measures by imposing those of England on Scotland.

Sir James Steuart, a Scottish economist, drafts “A Plan for Introducing an Uniformity of Measures over the World.” This is edited and published by his son in 1790.

1761 onwards
The opening of the Bridgewater Canal gives rise to a boom in canal construction. The Ramsden chain comprising 100 links each of one foot is adopted by engineers seeking accuracy with simplicity. (Author’s note. Ramsden chains were still around in the 1960s – we used one during a practical surveying course that I attended in 1963.)

1761 and 1769
The need for observations of the two transits of Venus results in a burst of unprecedented international scientific co-operation, with Britain taking a leading role. Will this continue for the world’s next great scientific endeavour – the development of a modern and internationally accepted measurement system?

James Watt tries to compare the results of his experiments on steam power with those from other countries. He writes to Irish chemist Richard Kirwan FRS: “I had a great deal of trouble in reducing the weights and measures to speak the same language; and many of the German experiments become still more difficult from their using different weights …” He also writes to Joseph Priestley FRS, and fellow member of Birmingham’s Lunar Society, asking him to encourage the scientists of England and France to cooperate to set up a common decimal system of weights and measures. Thanks to Kirwan’s international connections and Priestley’s contacts, Watt’s views are made known to the French Minister for Foreign Affairs, Talleyrand, and the eminent French scientist Lavoisier, both of whom play key roles in the creation of the metric system a few years later.

On 5 February, Sir John Riggs-Miller, MP for Newport, Cornwall, proposes in the House of Commons the reform of the English customary system of weights and measures in favour of a scientifically founded system. Two separate proposals from France suggesting collaboration on the creation of such a system are rejected by the British Foreign Secretary. Riggs-Miller loses his seat in Parliament at the general election later that year.

Sir Benjamin Thompson, Count Rumford, FRS, suggests that heat can be derived from motion (or mechanical energy), rather than, as was believed at the time, being a property of matter.

The UK is created by the Act of Union of Great Britain and Ireland. Irish measures are unaffected, but pressure on the Government to simplify the UK’s measurement muddle increases.

A Select Committee on Weights and Measures of the House of Commons reports.

A Royal Commission is appointed to consider more uniform weights and measures. In their first report, the Commissioners agree that a uniformity of weights and measures is obviously desirable, but link decimalisation of measures to decimalisation of the currency. It recommends simplifying English customary measures rather than using the metric system, at that time adopted only by The Netherlands including Belgium and Luxembourg.

The proposals of the Commission are the basis of the Weights and Measures Act 1824 and of the Imperial system that follows from it. This Act establishes standards for the primary units and ‘tidies up’ arcane laws without radically changing the multiplicity of customary weights and measures used throughout the country. Indeed, it expressly states that “it shall [be] lawful [to] buy and sell goods and merchandize (sic) by any weights or measures established either by local custom or founded on special Agreement” provided their exact relation to the standard units defined by the Act was generally known.
The USA retain English customary measures.

Gauss promotes the application of the Metric System, together with the second defined in astronomy, as a coherent system of units for the physical sciences. Gauss is the first to make absolute measurements of the Earth’s magnetic force in terms of a decimal system based on the three mechanical units: millimetre, gram and second. In later years, Gauss and Weber extend these measurements to include electrical phenomena, paving the way for the work of the British Association for the Advancement of Science in the 1860s and 1870s.

The standard pound and the standard yard are destroyed when the Houses of Parliament burn down.

A Royal Commission for the Restoration of the Standards of Weight and Measure is appointed. In its report, it refers to the advantages of establishing decimal currency in the UK, and goes on to say that this is required before reform of weights and measures could be undertaken.

James Prescott Joule, a Manchester brewer and physicist, publishes a paper proving the equivalence of thermal and mechanical energy and endorsing the work of Rumford almost fifty years earlier. (Recognising this, SI has one unit for both heat and mechanical energy, the joule; imperial has difficulty accommodating Rumford’s discovery and has two units, the British thermal unit and the foot-pound.)

The florin is introduced as the first step to the adoption of decimal currency, with ten florins to one pound.

The Great Exhibition draws attention to the advantages of a common international system of measurement.

The Decimal Association is set up to lobby for the decimalisation of both measurement and currency.
The Treasury decides that all cultivated rural areas should be mapped at 1:2500, an international standard which has the advantage of splitting the difference between 1:2640, or three inches to a furlong, and 1:2376, or one inch to three chains, hitherto much favoured for estate and similar surveys.

The 1:500 scale is prescribed for urban surveys instead of 6 inches to one mile. This decision and that of the Treasury a year before are not universally welcome, and in 1857 a House of Commons vote forces a temporary reversion to the six-inch scale. This is reversed a year later by a Royal Commission.

Joseph Whitworth (of screw thread fame) proposes a decimal measure of length for mechanical engineering, and the ‘thou’ is added to engineers’ vocabulary.
A British branch is formed of the International Association for Obtaining a Uniform Decimal System of Measures, Weights and Coins.

1861 – 62
The application of the metric system in the fields of electricity and magnetism is developed through the British Association for the Advancement of Science (BAAS), under the active leadership of two British scientists, J C Maxwell and William Thomson, later Lord Kelvin. The BAAS insists that electrical units should be coherent with the metric system and that electrical and mechanical energy should have the same unit, and proposes the additional metric prefixes of micro and mega.

A Select Committee of Parliament publishes a report unanimously recommending that the use of the metric system should be made legal but that “no compulsory measures should be resorted to until they are sanctioned by the general conviction of the public.”

The Weights and Measures (Metric System) Act permits the use of metric measures for ‘contracts and dealings’. It has little practical impact.

The Standards Commissioners, in their second report, recommend “That the time has now arrived when the law should provide and facilities be offered by the Government, for the introduction and use of metric weights and measures in the UK.” They add “Although there may be well-founded objections to the inconvenient length and occasional similarity of the French nomenclature, yet it is probable that these names will become familiar by custom … We think that the French nomenclature, as well as the decimal scale of the Metric system should be introduced into this country.”

A committee of the BAAS recommends using the CGS (centimetre-gram-second) system of units in science, and makes proposals for electrical units including electrical resistance. The CGS system becomes the basis for scientific teaching and research for the next seventy years; however, it includes two systems of electrical units, electromagnetic and electrostatic, which limits its practical use.

The UK sends a delegate to the conference that establishes The Metre Convention, but is not one of the original seventeen signatories.

The Weights and Measures Act abolishes the Troy pound and the pennyweight, effective 1 January 1879.

The first International Electrical Congress adopts many BAAS proposals for electrical units. These later become part of the metric system.

The British firm Johnson, Matthey & Co secures an agreement with the French Government to supply thirty standard metres and forty standard kilograms.

The United Kingdom becomes a signatory of The Metre Convention and joins the General Conference on Weights and Measures (CGPM).

One of the standard metres and one of the standard kilograms that had been cast by Johnson, Matthey & Co are selected at random as the reference standard, and pairs of the other standards, having been cross-correlated with each other, are distributed to the signatory nations of The Metre Convention. The UK receives the standards numbered “18”.

The first practical set of electrical units is proposed.

A Select Committee of the House of Commons recommends that the metric system should be authorised for all purposes, taught in elementary schools and become compulsory within two years.

A second Weights and Measures (Metric System) Act permits the use of the metric system for all purposes in the UK. Like the 1864 Act, this Act has little practical effect.

The adoption of the metric system in British workshops is proposed at the International Engineering Congress in Glasgow. It is said that, “from time to time, orders have been lost for hardware and textiles, owing to manufacturers not troubling to make them in the standards of other countries.”

Lord Kelvin leads a campaign for the adoption of metric measures, and delivers to Parliament a petition of eight million signatures.
The House of Lords debates metrication and votes to make metric compulsory after two years. The House of Commons fails to rise to the challenge.
The British Weights and Measures Association (BWMA) is formed “for the purpose of defending and, where practicable, improving the present system of weights and measures”.

A Select Committee on metrication recommends a compulsory changeover in 1910, and a Parliamentary Bill is drafted with to affect this. The government takes no action.

The Olympic Games are held in London. Track and field events take place at a new purpose-built stadium at White City. The Official Report says, “The introduction of the metric system is an innovation which may have proved some little inconvenience to British runners.”

The UK Met Office follows the lead of the International Meteorological Organisation (forerunner of the World Meteorological Organisation) and adopts the millimetre as the official standard unit of rainfall measurement.

The ‘British Grid System’ is adopted on military maps (not to be confused with civil mapping by the Ordnance Survey). In the military grid, areas are broken down into progressively smaller squares, with sides in turn representing 500 km, 100 km, 10 km, 1 km. Letters are allocated to the 500 km and 100 km squares and numbers to the 10 km squares, so that a point of reference can be given in letters and numbers. In 1927, it is modified and this system remains in use throughout World War 2.

Twenty-six Irish counties leave the UK.
The British Broadcasting Company Ltd is set up by six telecommunications companies. It begins transmitting public broadcasts from London using amplitude modulation of waves of constant frequency (and length). Radio sets that enable listeners to tune to a range of stations are calibrated by wavelength in metres. For some Britons, this is their first encounter with metric measures.

The Ordnance Survey initiates the re-triangulation of Britain in metric measures.

The Davidson Committee proposes that the Ordnance Survey uses a unified and kilometre-based national grid as a framework for all mapping of Britain. This proposal is adopted the following year.

The Olympic Games return to London, centred on Wembley.
At a meeting of representatives of Canada, the UK and the USA held in November at the National Bureau of Standards, Washington, it is agreed that the three countries will make the unified thread their first choice. This is a screw thread system introduced for defence equipment (1939-44), in which the thread form and pitch are a compromise between British Standard Whitworth and American Standard Sellers.

The Committee on Weights and Measures Legislation (the Hodgson Committee) concludes that metric conversion is inevitable, and that the long-term advantages which would flow from an organised change would far outweigh the inconveniences of the change itself (UK Department for Transport please note). It adds that, prior to the metric change, the currency should be decimalised.

The Prime Minister, Harold Macmillan, opens the M6 Preston Bypass, Britain’s first motorway. This has location posts at 100 metre intervals beside the hard shoulder.
Representatives from Australia, Canada, New Zealand, South Africa, the UK and the USA meet to discuss the possible adoption of a common definition for the inch, and hence the other imperial/USC units for length. A value of exactly 25.4 mm is agreed, to take effect in 1959.

A Joint Committee appointed by the BAAS and the Association of British Chambers of Commerce notes the world trend towards the metric system but finds insufficient support in British industry for making the change. In its report entitled, “Decimal currency and the metric system: should Britain change?” it concludes that there would be a 10 to 20 percent saving in mathematics teaching and a five percent overall saving in teaching time for children aged 7 to 11 years from the change.

The CGPM, including delegates from the UK, approves an updated version of the metric system, renamed the International System of Units (SI).
India, one of the UK’s largest export markets, announces that it will switch from imperial to metric.

The Met Office switches internally from Fahrenheit to Celsius. This had been adopted by the World Meteorological Organisation as the standard unit for temperature measurement.
The Government appoints a Committee of Inquiry on Decimal Currency (the Halsbury Committee). The Committee is concerned with the details of the introduction of decimal currency rather than the principle. It reports in 1963.

The Met Office switches to degrees Celsius for weather reports and forecasts for the general public, with Fahrenheit retained as a secondary unit to aid the transition “for a period of several years.” (It initially uses the obsolete term centigrade).
The British Standards Institution (BSI) issues a statement, “Change to the metric system?” setting out the main issues, and this is widely circulated in industry for comment.
The final report of the Molony Committee on Consumer Protection states, “A uniform system of weights and measures, nationally used and enforced, is plainly part of the basic vocabulary of consumer protection.”

In October, BSI publishes “British industry and the metric system”, summarising the results of its consultation with industry. This shows that a large majority is firmly in favour of starting a change to the metric system without delay and without waiting for the rest of the Commonwealth and the United States. The report concludes that there is a unanimous desire for decision and that indecision was “acting as a curb to industrial progress”.
The Weights and Measures Act ends reliance on national physical standards for imperial measures of length and mass and introduces the following definitions:
1 yard = 0.9144 metre,
1 pound = 0.453 592 37 kg.
(For capacity, the 1824 definition of the gallon as the volume of ten pounds of water does not change, although it is linked to the metric system as a result of the redefinition of the pound and the inch.)
Many imperial measures are no longer legally authorised. These include the drachm, scruple, minim, chaldron, quarter (of a hundredweight) and rod (or pole or perch).

In February, the President of the Federation of British Industries (now the CBI) tells Ministers that the majority of its members are in favour of the adoption of metric as the primary measurement system.
In May, in response to a parliamentary question, the Government announces that they “… consider it desirable that British industries on a broadening front should adopt metric units sector by sector, until that system can become in time the primary system of weights and measures for the country as a whole …” and that “the Government hope that within ten years the greater part of the country’s industry will have affected the change.” The programme would be voluntary and costs would be borne where they fell.
In November, major sectors of British industry approve a policy statement that urges British firms to regard the traditional screw thread systems – Whitworth, BA and BSF – as obsolescent, and to make internationally-agreed ISO metric thread as their first choice (with the ISO Inch (unified) thread as second choice) for all future designs.

The government announce that decimal currency will be introduced in 1971.
The BSI and the Ministry of Technology issue Handbook 18, “Metric standards for engineering”, to be applied to all products that will be exported to Common Market countries.
A Parliamentary Standing Committee on Metrication is appointed.

BSI publishes a report, PD 6245 “Going metric – first stages”, setting out the background to the change, how standards will be provided, how the change should be programmed and the role of Government. It also suggests that SI, rather than metric technical units, is the logical system for the UK.
The education system starts moving to metric units following the publication of guidance by the Department of Education and Science (DES).
The agreed timetable for the metric changeover in the construction industry is published.
International paper sizes begin to replace old favourites such as foolscap, quarto and letter.
The UK Hydrographic Office begins a programme of metrication of nautical charts and the conversion of depths to metres – the scales of charts are already decimal.

Following a conference of editors of journals relating to science and technology, The Royal Society publishes agreed recommendations. These are that SI should be used in journals in preference to Imperial, CGS or metric technical units, and that the changeover should be made as quickly as possible.
The BSI publishes policy document 6424, “The adoption of the metric system in engineering: Basic programme and guide.”
The DES arranges several conferences to consider the consequences of moves in the education system towards SI units, and away from CGS units in scientific subjects.
In July, the setting up of a UK Metrication Board is announced.

From 3 March, the metric system becomes obligatory for the dispensing of prescriptions; bottled medicines are accompanied by 5 mL spoons.
The Government announces that speed limits will go metric in 1973.
The UK Metrication Board is appointed and on 28 May holds its first meeting under the chairmanship of scientist and broadcaster Lord Ritchie Calder. Its task is to facilitate the UK’s transition to the metric system, and its role is “advisory, educational and persuasive” with no power to force change. Its first report “Going metric: first five years, 1965-69” begins with the words, “Britain will be a metric country before 1975.”
Examinations for students starting higher education courses in science, engineering or technology are set in SI units.

1969 – 75
The building and construction industries progressively adopt SI, beginning with dimensional co-ordination, product development and then project design, finally moving on to construction on site.

BSI completes the metrication of 1200 British Standards, and the Government agrees to fund the redrafting in metric terms of a further two thousand.
In September, the UK Hydrographic Office adopts the international nautical mile of 1852 metres in place of the UK nautical mile of 6080 feet (1853.18 m).
The Met Office drops values of temperatures in degrees Fahrenheit from official reports.
In October the House of Commons debates metrication, and the Government announces that there will be a White Paper on the subject.
In December, the Minister for Transport Industries is asked in Parliament “if he will state the estimated cost involved in alterations to vehicles and road signs of all kinds if metric distance and speed measurements are introduced into this country.” He replies, “Nearly £2 million for speed limit signs: the Government have however decided that speed limits will not be made metric in 1973 and have no other date in mind.”
The Commonwealth Games adopt the metric system for all events.

Decimal currency is introduced on 15 February.
All examinations conducted under the auspices of the Council of Engineering Institutions are in SI units.

The White Paper on Metrication (Cmnd. 4880) confirms that metric units should become the primary system of measurement in the UK, and says that the changeover should take place in a well-ordered and regulated manner.
The Building Regulations are re-issued in metric units to match progress in the building industry.
British Steel switches to metric. From April steel is sold in tonnes, with dimensions for most products in metric units.

The UK joins the European Economic Community (EEC), accepting a commitment to adopt the metric system.

Maths teaching in metric in primary schools is now the norm – science has been taught in metric since the turn of the century.
The Ordnance Survey begins the publication of 1:50,000 Landranger map sheets replacing the One Inch Seventh Series, and effectively ending the “Battle of the scales” that had begun in the eighteenth century.
Metric measurements are given on clothing labels.
The International Rugby Football Board announces that from 1975 all measurements in the game will be metric, for example the 25 yard line will become the 22 metre line and the 5 yard line will become the 5 metre line.

Rail traffic goes metric, switching from imperial tons to tonnes.
Royal Mail changes to metric weights for postal tariffs.
Tea, sugar, milk, soft drinks and other essentials begin to appear in rational (‘hard’) metric packaging in grocers and supermarkets.
Other voluntary retail initiatives include the pricing of floor covering and carpet in metric.

The Imperial gallon is redefined as 4.546 09 dm³.
The Weights & Measures etc Act provides powers to plan for an orderly change to the metric system and to phase out certain imperial measures. It has the support of every consumer organisation in the UK, including the Consumer Association, the National Consumer Council and the National Federation of Consumer Groups, as well as the Confederation of British Industry (CBI) and the Trades Union Congress.
A report by the US National Aeronautics and Space Administration (NASA) notes that the metrication programme lacks leadership from the UK government. This conclusion is echoed in a report in 1979 by the US National Bureau of Standards.

Speedometers on all new vehicles are required to be marked in mph and km/h.
A major carpet retailer (now no longer in business) finds enormous commercial advantage in reverting to sales by the square yard because these prices appear to customers to be 20% cheaper than those in metric. Metrication of carpet sales enters into a full-scale reverse. It is realised, belatedly, that a voluntary approach to the retail changeover does not work. Retail associations press the government for cut-off dates for imperial pricing of a wide range of products.

The furlong, cubic yard, bushel and dram cease to be legally authorised.
The government estimate that the cost of converting road traffic signs would be £7.5 to £8.5 million.
A small number of critics in each political party in Parliament voice opposition to the element of compulsion in the metric changeover, and the Government delay seeking Parliamentary approval for an order setting a clear retail cut-off date.

There is a change of Government, and on 14 November the new Consumer Affairs Minister announces that the Metrication Board will be dissolved on 30 April 1980 and that further metrication should be “on a voluntary basis”.

The square inch, square mile, cubic inch, cubic foot, hundredweight, ton, horsepower and Fahrenheit cease to be legally authorised.
The UK Metrication Board is abolished. The Government says that “metrication has now been extensively adopted in manufacturing industry and also in retail trade, where most packaged goods sold in prescribed quantities are now sold in metric sizes, so there is now very limited scope for the Board’s activities …”
The metric transition stalls.

1980 onwards
Manufacturing industry, which had been slow to adopt metric measures, now sees its export markets shrink as other countries of the former British Empire complete the metric transition. Although this is not the only factor contributing to Britain’s industrial decline, it is a significant one. Hard hit is the West Midlands, the birthplace of the industrial revolution.

On garage forecourts, pricing per litre is permitted. This had been requested by garage owners to enable an extension of the life of older pumps, many of which are limited to a maximum price of only £1.99 per unit. Equivalent prices per imperial gallon must be shown alongside the price per litre.

The Weights and Measures Act 1985 enables many imperial units to be dropped from use for retail sales by weight or measure. It also redefines the imperial gallon as 4.546 09 litres exactly. It does not cover goods and services sold by description, for example a “32 inch TV” or a “five foot Christmas tree”.

The Units of Measurement Regulations transpose directive 80/81/EEC (the units of measurement directive) into UK law.
Foreign-owned manufacturing companies see the potential of the UK: located inside the EEC tariff wall, English speaking and possessing a skilled work force and a supply chain that is adapting to metric production. Nissan is among the first to become established, opening a pioneering car production plant in Sunderland.

A British scientist, Dr Terry Quinn CBE FRS, becomes the Director of the International Bureau of Weights and Measures (BIPM).

The EEC agrees to a postponement of the completion of the UK metric changeover.
Honda opens a factory in Swindon to produce car engines.

Toyota opens a plant to build cars in Derby and Honda opens one in Swindon.
Metric units are substituted for, or permitted as alternatives to, imperial units in many regulations. As an example, domestic gas consumption can be charged by the kWh instead of by the therm.

The UK Hydrographic Office announces that it is able to provide data in digital format for those charts which show depths in metres.
Boeing cancels its project to build an ultra-high-capacity airliner (UHCA). This creates a gap in the market which is subsequently filled by the Airbus A380.

In July, regulations are laid before Parliament relating to metric units of measurement and their use for weights and measures and price marking purposes.
Retailers of carpets and floor coverings prepare, for the second and final time, to switch to pricing per square metre.
The last pumps at filling stations that are calibrated in gallons are converted to litres or replaced.
The Traffic Signs, Regulations and General Directions (TSRGD) 1994 allow but don’t require metric measurements on signs which impose height restrictions.
BMW acquires the Rover Group, including the Mini brand. It later switches production of the Mini from Longbridge to a rebuilt plant and new production line at Cowley, Oxford.

All imperial units cease to be primary measures, except for eleven units when these are used for specific purposes. Many familiar units, including the square foot, square yard, cubic foot, quart and gallon, though still able to be used, are no longer legally authorised.
In pubs, spirits must be served in metric quantities eg 25 mL, 35 mL.
On garage forecourts, equivalent pricing per gallon is no longer obligatory.
Regulations prescribe rational metric sizes for many pre-packed goods.
New gas and water meters show consumption in cubic metres, although some existing gas meters showing cubic feet may well survive until 2020.
Some non-SI units required by international treaties in air, sea and rail transport remain in use without time limit, for example the nautical mile, knot and foot (for altitude).
In July, the Department of Trade and Industry (DTI) publishes a report, “The adoption of the International System of Units as the primary system of measurement in the UK.
The British Weights and Measures Association is re-launched “to protect and promote British weights and measures, and to oppose compulsory use of the metric system”.

Supermarkets, butchers, fishmongers, grocers, greengrocers and corner shops complete their preparations for the switch to weighing and pricing in metric.

The therm, fathom, gill and fluid ounce are no longer legally authorised.
Weighing for retail sale using imperial measures of either ‘loose goods’, for example fruit and vegetables, or ‘from bulk’, for example meat and cheese, is no longer permitted and metric prices must be displayed. Customers are still able to ask for pounds and ounces, and supplementary pricing in imperial is also allowed, so it is only traders that are affected. A few find difficulty weighing or pricing in metric.
Croydon Tramlink opens with metric speed limit signs.

A group is formed with the aim of removing road signs which it considers fall outside the traffic signs regulations because they show metric measures. It achieves publicity the following year after its founder is convicted of theft and criminal damage when about 40 signs are removed in Kent. The conviction for theft is overturned on appeal after the signs are recovered.
Four traders are convicted under the Weights and Measures Act or the Price Marking Order for failing to weigh goods in metric or to price goods in metric alongside imperial.

The four traders who were convicted in 2001 for failing to weigh or price goods in metric together with one other trader lose their appeal against their convictions.
The TSRGD 2002 allow, but do not require, metric measurements on signs which impose width restrictions.
The Government say changing road signs would be confusing for drivers who had not received a metric education at school, and use this as a reason for postponement.
The UK Metric Association (UKMA) is formed.

The DTI, the British Standards Institution and the CBI publish the “Final document” and “Implementation annex” of the National Standardisation Strategy Framework (NSSF) – a joint attempt to improve the UK’s economic performance by harmonising standards. UKMA considers that the NSSF misses the point – standards can only be harmonised if everyone uses the same measurement system, and the following year it publishes its response entitled, “A very British mess”.
Driver location signs that complement distance marker posts are introduced experimentally on motorways and major highways.

Professor A J Wallard CBE takes over from Dr Quinn as Director of BIPM in Sevres, Paris, moving from the UK National Physical Laboratory (NPL).
Traders convicted in 2001 lose their appeal at the European Court of Human Rights. One dies of a heart attack, becoming anti-metric campaigners’ first ‘metric martyr’.

Over a single week-end in January, the Republic of Ireland completes the metric conversion of its road signs by changing all speed limit signs – distance signs had been converted gradually over the previous decade. For the first time, the UK has a land border with a country that uses a different measurement system on its road traffic signs.
Prescribed quantities are abolished except for alcoholic drinks.
MG Rover Group, formerly British Leyland, goes into administration bringing an end to mass car production by British-owned manufacturers – with MG and the Austin, Morris and Wolseley brands becoming part of China’s SAIC.

The UK Department for Transport (DfT) publishes an estimate of the cost of converting road traffic signs for distance and speed. The estimate for speed limit signs is about 180 times the one prepared in 1970 – ‘gold plating’ is suspected.
UKMA publishes its report, “Metric signs ahead”, on the conversion of road signs, together with its estimate of £80 million (in contrast to the DfT’s £700 million).

In October, the Airbus A380 enters commercial service. Major structural sections of the Airbus are made in France, Germany, Spain and the UK (wings and engines) and then assembled in France.
In November, the Channel Tunnel Rail Link with metric distance and speed limit signs opens from the Channel Tunnel to St Pancras International.

Nic Davison is served with an infringement notice for selling draught beer by the litre at his Polish restaurant in Doncaster. He refuses to change, and eventually the case against him is dropped.
The National Weights and Measures Laboratory issues an “Update on metrication”, saying it is “keen to encourage [enforcement] action that is proportionate, consistent and in the public and consumer’s interest.” It adds, “Consistency of units allows customers to make value-for-money comparisons with similar goods on offer.”
Sales of canned and bottled beer exceed those of draught beer for the first time.
The European Parliament approves an amended measurement directive. The UK Government then claim credit for “saving the pint and the mile”.
The DfT sets up the Traffic Signs Policy Review, heralding it as the “the biggest review of British road signs for forty years.” The review runs from September 2008 to May 2011, but does not consider metrication policy and achieves little.

At the end of the year, the acre ceases to be a primary unit.

The use of supplementary indications is permitted indefinitely, as well as the use of six imperial units for specific purposes only:
* the mile, yard, foot and inch for road traffic signs, distance and speed,
* the pint for draught beer and cider, and doorstep milk, and
* the troy ounce for trading in precious metals.

The Traffic Signs (Amendment) Regulations and General Directions 2011 allow optional dual (metric and imperial) triangular signs warning of height or width restrictions, and require the internationally-recognised symbol “t” for tonne to be used on new weight limit signs.

Preliminary results of the 2011 census show that a majority of the UK population has been taught using metric measures at school.
The London Olympics raise the profile of metric measures in millions of UK homes.

Dr M Milton follows in the footsteps of Professor Wallard, moving from the NPL to become Director of BIPM.
The Government admit that failure to convert road traffic signs may require changes to the school curriculum.
Network Rail confirms that the progressive installation of the European Rail Traffic Management System (ERTMS) on selected routes over a twenty year period will see the end of the mile, chain and yard on much of the British railway network.

The DfT announces that Highway Authorities will not longer be permitted to erect new imperial-only vehicle height and width restriction signs.
The Commission considering the Scottish devolution recommends that control of speed limits and road signs be passed to the Scottish Parliament.
UKMA publishes a report entitled “Still a mess“, covering the results of an opinion survey carried out at its request in 2013 by YouGov.

The Traffic Signs Regulations and General Directions 2016 came into force on 22 April 2016. It makes metric units mandatory (alongside imperial units) for all new vehicle dimension signs.