For the last three months, the UK has been wallowing in nostalgia. The population has taken to their deckchairs, put knotted handkerchieves on their heads, written letters to their cousins in Sydney and Auckland, and engaged in that wonderful pretence that it’s still the 1930s, or perhaps the 1890s.

It’s as if sitting in a wood-and-leather compartment being towed by a steam locomotive has suddenly dispelled all the problems of the modern world. The former British Empire is back, we can pick up the reins which Queen Victoria dropped when she died in January 1901, and we can finally teach those upstarts in Europe that we are still a power to be reckoned with, outside its porous borders.

In among the aspidistras in this conservatory of times past, all sorts of hare-brained schemes are being put forward. Among the latest is the repeal of laws requiring the use of metric measurements, and re-instatement of imperial units in their place. How quaintly appropriate: imperial units.

Before you roll on the floor in laughter, this is a serious proposal, and one which would probably attract considerable support in UK parliament. Certain newspapers, which are clearly stuck in the 1930s or 1890s, such as The Telegraph and the Sunday Express, seem to think that it is a good idea too.

Before you bask in the warm glow of nostalgia at buying sweets in quarter pound bags and petrol by the gallon, I’d just like to draw attention to some basic facts about measurement systems.

Measurement systems must above all else be consistent and unambiguous. The UK is largely metric, and where it counts most has adopted the International System of Units, SI.

In a few everyday measurements, we still use non-metric units: miles, miles per hour, and pints, are the most common. They co-exist because there are few areas in which there is ambiguity. When you see a road sign bearing the figure 30, there is no doubt that it refers to 30 miles per hour. When you order a pint of bitter, there is no doubt as to the volume of beer which you should receive.

Revert to more non-metric units, and chaos quickly ensues. When you only use metric, and go for a length of timber, it is not difficult to know that you want three metres, not centimetres, millimetres, or kilometres. If you mix imperial and metric, it could be three feet, metres, or yards.

The same goes for temperature. Currently, anyone in the UK who is remotely numerate would recognise that a hundred degrees means Celsius (not the SI base unit of Kelvin, particularly if we refer to degrees), although a few may still think those degrees are Centigrade. Use Fahrenheit alongside, and disaster can ensure: 100˚F is pleasantly warm to the touch, 100˚C is literally boiling and ready to injure the skin. Get the wrong unit, and your dinner may have only just defrosted, or could be burned to a cinder.

Mixing metric and imperial is not only error-prone, but horribly inefficient. One of the tedious tasks which I have to do for this blog is to quote dimensions of paintings in centimetres, although many are originally provided only in inches. Furthermore, I check whether the dimensions provided appear correct, and in many cases discover that when both inches and centimetres are provided, they do not correspond – conversions have been performed incorrectly, such as dividing by a conversion factor rather than multiplying.

So proposals such as allowing retailers to state quantities in either metric or imperial units are a road to disaster. If you see one cereal product being sold at £4 per pound, and another at £0.80 per 100 grams, which is the cheaper?

Our current EU and national law permits expression in non-metric units, provided that it is accompanied by a conversion to official units. You then realise that the first cereal would cost you £8.82 per kilogram, whereas the latter is only £8.00 per kilogram. Allowing a retailer to conceal that information only impedes consumer choice, to the advantage of the retailer.

Although there are still some countries in the world, the USA most notably, which retain many non-metric units in everyday use, there is no country in which non-metric units of measurement prevail – apart from Burma, which apparently still uses its own traditional system. US measurements for fluid volume (fluid ounces, pints, quarts, and gallons) are different from old UK imperial units too, so we couldn’t even claim any consistency there.

Like it or not, science, engineering, medicine, and most of industry throughout the world now uses metric units. You can hide behind as many aspidistras as you like, but every doctor around the world prescribes drugs using units like milligrams, and must continue to do so. Again, there are some important international exceptions, in nautical miles (which are different from UK land miles, of course), knots (nautical miles per hour), and aviation altitudes (which are still based on feet).

It is also most telling that those proposing a return to imperial units claim that metric units are French, and imposed on the UK by the EU. It is correct that some units in SI had origins in France, but SI itself is truly international. Celsius was the combination of proposals by two Swedish and one French scientist. Kelvin was proposed by, and named after, a British physicist who was born in Belfast and trained in Scotland. The second has origins across cultures, but was first formally proposed by the British Association for the Advancement of Science.

In the UK, the first move towards a metric system of units was proposed by John Wilkins in 1670. James Watt called for an international metric system to be developed in 1783. In 1818, a Royal Commission reported to Parliament on metrication and the decimalisation of the UK currency, and that debate continued off and on until 1896, when the UK finally accepted metric measurements as having a legal basis. In 1968, the UK government announced the formation of the Metrication Board, which would oversee conversion to the metric system, to be completed by the end of 1975.

Meanwhile other members of the Commonwealth, which had agreed to metricate, got on with the job: Australia, New Zealand, and South Africa were all completely metric by 1980. None of those three countries is a member of the EU, and none was forced to metricate. As with every other nation including the UK, they recognised the necessity and inevitability of doing so.

The UK has not metricated because any organisation told it to, but because to persist in using irrational, error-prone and impractical units of measurement would be futile and damaging to the nation. The proposal to revert to imperial measurement makes as much sense as reverting to Norman French as the official language in our courts and administration.

The case for demetrication is also a model of that for leaving the EU. We are becoming obsessed with means and processes without having any idea as to where they might take us.