Two widely-shared tweets from Eurosceptic think tank the Bruges Group, which claim the European Union forced the UK to use the metric system by making it a criminal offence to use imperial units, do not tell the whole story.
The tweets were posted in late May as a response to the government’s announcement of a consultation on whether to remove the requirement for most goods to be sold in metric units.
The first tweet said: “Imperial measurements have been part of Britain’s social fabric for generations. Their use never should have been outlawed at the behest of foreign bureaucrats.”
A later tweet by the same group added: “All that has been done is that the use of imperial measurements is being decriminalised (and just let that sink in, the European Union actually made using Imperial measurements a criminal matter).”
It is true that using imperial measurements alone generally became illegal when selling packaged goods in 1995 and loose goods in 2000, and some individuals who became known as the ‘metric martyrs’ were prosecuted for doing so. But it is not accurate to say that the EU or its forerunner the European Economic Community (EEC) outlawed or criminalised all imperial measurements.
Special exemptions mean some measurements, such as pints for beer and miles for road distances, have always been legal to use. Imperial units can also be used as a "supplementary indication" alongside metric units in all situations, so long as they are not given greater prominence.Finally, it’s worth noting the UK did take steps towards switching to the metric system prior to joining the EU.
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How the UK moved to metric
The decision to start adopting the metric system was taken before the UK first joined the EEC in 1973.
A switch to the metric system was discussed in the House of Commons as early as 1863. More than 100 years later, on 24 May 1965, Douglas Jay, at the time Economic Secretary to the Treasury, outlined plans to MPs about making the metric system the main one in use across the UK.
He said that the government considered 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”.
Primary schools began teaching the metric system in 1970, three years before the UK joined the EEC, but continued to teach imperial units at the same time, requiring students to learn both systems.
European law or UK law?
When the UK joined the EEC, the existing European legislation on weights and measures was amended to take into account the fact that the UK used imperial units.
The UK’s Units of Measurement Regulations in 1994 amended the Weights and Measures Act 1985 so that from 1 October 1995 the metric system was required for retail sales of packaged goods. This law was then extended to loose goods, such as vegetables, in 2000.However even when these changes came into effect, retailers could continue using supplementary imperial measurements alongside metric ones. And the law also allowed for the sole use of certain imperial measurements, such as pints for beer, acres for land registration and miles for road signs.
An EU directive had called for a complete ban on the use of dual labelling after 1 January 2000, but the Department of Trade and Industry (DTI), as it was then, chose not to include this ban in UK’s regulations of the time amid fears it would damage exports to countries such as the USA that were still using imperial measures. The DTI said it hoped this part of the legislation would be dropped.
In 2007 the EU announced it no longer intended to pursue this part of the directive, allowing the UK to continue using dual measurements and some specific imperial measurements indefinitely.
Europe's Industry Commissioner Gunter Verheugen said in 2007: "There is not now and never will be any requirement to drop imperial measurements."
He further promised that the European Commission would never “be responsible for banning the great British pint, the mile and weight measures in pounds and ounces”.
An old section of the European Commission website devoted to correcting stories in the UK media about the EU stated in 2016 that the EU “never banned pounds and ounces or other imperial measures”.
In another entry, from 2001, it said: “It is not a criminal offence to sell goods in imperial. Traders are allowed to display weights and prices in both imperial and metric but not in imperial only. Consumers can continue to express the quantity they wish to buy in pounds and ounces. The directive was agreed by the UK Government of the day and the implementing legislation was approved by Parliament in Westminster.”
As mentioned above, a number of traders—dubbed the ‘metric martyrs’—were prosecuted and convicted for using scales or displaying goods in imperial units only. But although it is the case that using imperial units alone is against the law in most cases, it is not illegal to use them if traders include metric prices on their displays as prominently as the imperial measures. They also have the option of providing the metric equivalents of whatever imperial measure customers ask for.
So while it has been illegal to sell most goods using imperial measurements alone since 2000, the EU did not outlaw their use altogether.