PM opts for outdated measures
It is now more than fifty years since Parliament voted for the United Kingdom to adopt the Système International of weights and measures. After half a century of using metres, litres and kilograms, the Prime Minister proposes to get the country heading back to the days of selling stuff in pounds (lb) and ounces (oz).
This is the latest example of “taking back control,” much vaunted by those eager to see the UK free itself from bullying by Brussels. But this betrays the total lack of historical intelligence in those calling for this change. It flies in the very face of the idea of “Global Britain.”
Origin of the metric system
The metric system was devised in France, following the Revolution of 1789. Up until then France used a system very like our own. They had a “pied” (foot) of twelve “pouces” (thumbs). Their currency was the “livre” (pound) made of twenty “sous”. The sous consisted of twelve “deniers.” And right there you have “L S D”!
The revolutionaries had all sorts of ideas for measuring everything using the base 10. For a brief time they divided the year into twelve months, each of three decades of days. and gave their new months new names. These, such as “brumaire,” based on the French word “brume” meaning mist, reflected the season of the year. It won’t surprise you to learn that brumaire coincided with November.
The French decided that the mile had no logic. The name had its origin in the ancient Roman “mille passus” or thousand steps. But it no longer bore any clear relationship with this distance.
So their learned men at the Académie Française set about measuring the circumference of the globe along the meridian which passes through Paris. They took a quarter of this length and divided it by ten million, which gave them one “measure” or “mètre.”
Because the metre didn’t have unpredictable fractions, as the mile did, but scaled up or down by a factor of ten, it was readily adopted, not only by France, but by the majority of countries around the world.
Confused? You already are!
So, why did the United Kingdom change from the system which had stood us in good stead for centuries? The answer is simply, “trade.” The British system – generally known as the Imperial system – had been exported to all the colonies. But the colonies, keen to trade with other parts of the world, had abandoned it in favour of the metric system.
[ Link to the Government White Paper on Metrication (1972) ]
So businesses in the United Kingdom were bringing greater pressure to bear on the government. They wished to adopt the same system also in order to trade with the rest of the world. It was an attempt to keep Britain “global” and had nothing to do with the EU. In fact at that time there was no prospect of our even joining what was the EC, the European Communities.
Half-hearted, as usual
While the UK proceeded to adopt the latest version of the metric system, the Système International, in principle, in practice it was a very different matter. The Act specifically required certain items to continue to be sold in traditional amounts. So our milk and our beer continue to be sold by the Imperial pint. This now leads to both liquids being available in both Imperial and SI measures.
While civil engineers freely use metres and kilometres to measure our highways, direction signs stubbornly display distances in miles. Our speed limits are still obtusely displayed in miles per hour (mph) and not kilometres per hour (km/h).
Mix and match
And yet… Along the edge of motorways and primary routes there are little posts sticking out of the ground. One of their purposes is to direct you to the nearest emergency telephone.
In the earliest days of motorways they were spaced 110 yards apart. There were sixteen of them to the mile, and they would appear as eg 32/12. This meant that this post was 32 miles and 1 320 yards (or 6 furlongs) from the designated origin, eg Charing Cross in London.
But around the middle of the ’80s they were replaced by metric markers, spaced 100 metres apart. (Note: 100m is just a touch less than 110 yards.) Our 32/12 moved slightly and morphed into 52/7, or 52.7 kilometres from the origin.

M20 / B / 61.5
In addition, since 2003 we have seen an increasing number of “Driver Location Signs,” each bearing a unique identification. As an example you might see on an upright rectangular plate the legend M20 / B / 61.5. This information is sufficient to tell the emergency services precisely where you are to within 500m.
The M20 is obvious: you’re travelling on the motorway with that number somewhere in Kent. The B specifies your direction of travel. In this case it is towards London. An easy way to remember is that the A carriageway takes you Away from the road’s origin, and the B carriageway takes you Back. (Other letters appear on connecting ramps, and M26, which joins M25 and M20 uses K and L. One enthusiast has suggested that K is “towards Kent”, and L, “towards London”.)
But, what’s the “61.5” all about? That’s the distance in kilometres and tenths from the origin.
True birth weight
Proud parents return home from the maternity ward bearing their new bundle of joy. “How much did she weigh?” the neighbours ask. “m pounds and n ounces,” reply the joyous parents, unaware that their offspring were actually weighed in kilograms. The hospital obligingly translated it for them into Imperial weight. But they sometimes get it wrong! They misread the conversion table, and so misinform the family. The true birth weight is the one recorded in kilograms.
No advantage
There is no clear reason to reintroduce Imperial weights and measures, or even to encourage market traders to use them. A whole generation has grown up educated to use metric. Sixty years ago commercial exercise books were printed with tables of weights and measures on the back. So you could check how many pints there were in a gallon, how many chains in a furlong, or how many feet in a fathom.
Or is this proposal a vain attempt to regain our former Imperial glory? Whatever next? Reversion to the old £ s d? That’ll be as welcome as a mouse at a Mothers’ Union meeting!