Ronnie Cohen

The Use of SI Units – Why a 60‑year‑old BSI publication still matters for Britain’s future

Britain has lived with a measurement muddle for generations—yet the solution has been sitting on our shelves since 1965. The Use of SI Units, published by the British Standards Institution, is one of the most quietly influential documents in UK technical history. Far from being a dusty relic, it offers a clear, practical, and forward‑looking blueprint for a fully metric Britain—one that engineers, teachers, policymakers, and ordinary citizens can still benefit from today.

What makes this publication remarkable is not just its technical clarity, but its vision: a UK where measurement is simple, coherent, and internationally aligned. Amid the decades=old debates for and against metrication, this BSI report deserves a fresh look. It shows how much we’ve already achieved—and how much further we can go.

Report on Going Metric: How? Why? When?

During the late 1960s and 1970s, British industry embarked on one of the most significant technical transitions in its modern history: the move from imperial to metric units. This shift—often described simply as “going metric”—was not a sudden revolution but a carefully staged programme of industrial modernisation. The materials reproduced in the “Going Metric: Industry is changing to the metric system of Weights & Measures. How? Why? When?” report, originally issued by the Ministry of Technology and the British Standards Institution, reveal a campaign that was both practical and persuasive. It aimed to explain the logic of metrication, prepare engineers and designers for new working methods, and reassure the public that the change would be orderly, beneficial, and internationally aligned.

What emerges from the report is a clear narrative: metrication was not merely a change in units, but a strategic response to globalisation, industrial efficiency, and the need for standardisation across sectors. This report synthesises that historical material to provide a coherent account of how industry was expected to change, why the change was considered essential, and when the transition was planned to occur.

British Exceptionalism and the Long, Strange Story of UK Metrication

Few policy areas reveal the UK’s distinctive relationship with European integration as clearly as measurement. Metrication — a technical, administrative reform everywhere else — became a cultural battleground, a sovereignty symbol and ultimately a microcosm of British exceptionalism in the UK.

This article traces how the UK’s wider pattern of exceptionalism inside Europe shaped, distorted, and ultimately stalled the UK’s metrication journey. It shows why the UK ended up with a uniquely very British measurement mess, why road sign units are predominantly imperial and why pints remain politically untouchable. And it explains how a seemingly mundane reform became entangled with national identity, Euroscepticism, and the story that culminated in Brexit.

Media blast from the past

In the early years of the Metrication Programme, which began in 1965, the press was not hostile to metrication. They published articles that sounded supportive or neutral. It was only a couple of decades later when metrication progress ran out of steam and the consensus on metrication broke down in the 1980’s that the press turned against metrication. Here we look at some of the earlier and later newspaper articles that reflect the changing attitudes to metrication in the UK.

Why UK Metrication Programme failed according to AI

I consulted Microsoft Copilot to ask its opinion on the reason for the failure of the UK Metrication Programme. I asked it, “The UK started the Metrication Programme in 1965 and planned to complete metrication in 10 years. Why has the UK failed to complete its transition to the metric system? What went wrong?”. It gave great insights into the factors that caused the UK to fail. Its response, with AI formatting and emphasis, is reproduced below.

The old Swedish decimal measurement system

The English bishop John Wilkins was not the only one who developed a decimal-based measurement system that predates the metric system. Anders Bure, a Swedish mathematician and cartographer who lived from 1571 to 1646, developed a different decimal system that used the Swedish foot as the base unit. He tried to introduce this system of weights and measures in Sweden in the seventeenth century. Georg Stiernhielm, a Swedish civil servant, linguist and poet who lived from 1598 to 1672, later recommended this system should become the standard. This system was used between 1855 and 1889. Then Sweden changed over to the metric system on 1 January 1889.

DfT excuse for promoting unauthorised imperial signs in the TSM for the last 9 years

When the latest Traffic Signs Regulations and General Directions (TSRGD) came into force in April 2016, imperial-only restriction signs for height, width and length were no longer authorised. However, the Traffic Signs Manual (TSM) that provides guidance to road contractors on signage has not been updated since 2009 and still includes imperial-only restriction signs to this day. Six months ago, I asked my local MP to contact the Secretary of State for Transport to ask why the Department for Transport has been promoting the use of unauthorised imperial-only road signs since 2016. I received a reply from the DfT a few days ago.

Recent example shows way to beat hostile press on metrication

On 19 May 2025, the UK concluded a new agreement with the European Union amid cries of betrayal from the pro-Brexit press. While UKMA has no position on UK-EU relations or on this new agreement, it is a case study to show how it is possible to implement policies such as the completion of the Metric Programme, which started in 1965, while resisting attacks from a hostile media.

Happy 150th anniversary to the Metre Convention

Today is exactly 150 years since the Metre Convention was signed by 17 nations. This treaty established the use of the metric system internationally and created the International Bureau of Weights and Measures (BIPM), the General Conference on Weights and Measures (CGPM) and the International Committee for Weights and Measures (CIPM), organizations with different roles, to co-ordinate international efforts to standardize measurements.

HAPP one-day conference on the history of measurement

The St Cross Centre for the History and Philosophy of Physics (HAPP) is holding a one-day conference on the history of measurement at the Mathematical Institute in Oxford on Saturday 7 June 2025 from 10.30 am – 5.00 pm BST. Participants can register to attend in person or online. Everyone is welcome to attend. Registration to attend this conference is free but booking is required to attend the conference in person or online.

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