This announcement was the result of strong lobbying by the Federation of British Industry (now CBI) who wanted Britain to adopt the metric system in order to be internationally competitive. This decision had cross-party support and was seen – along with decimalisation of currency – as a welcome modernisation. It also had nothing to do with Britain joining the EEC eight years later, though when Britain joined in 1973 it simply confirmed its existing policy to adopt metric.

In 2005, despite industry using the metric system almost exclusively since the 1970s and two generations of metric-educated children, Britain is in a part-metric, part-imperial measurement mess.

Beer is sold in cans and bottles with metric sizes but must be sold draught in pints. Road signs and roads are designed in metric but road signs must show distances and restrictions in imperial. Children learn metric in the classroom but face imperial outside the school gate. Walkers using Ordinance Survey maps use a kilometre grid but have footpath signs marked in miles and yards.

In 1971, Britain made a rapid, compulsory and effective switch from pounds shillings and pence to decimal currency. This was achieved through a very good changeover plan supported by lots of information for the general public. Every household in the UK was issued with an information booklet and in the final stages there were information programmes on radio and TV. The public had a "sharp shock" but very rapidly mastered the change and never looked back.

Despite the successful example of decimalisation, successive governments have planned the metric changeover using exactly the opposite approach.

The initial plans were diluted and replaced with voluntary measures in the retail sector. Various derogations (temporary opt-outs) were negotiated to delay introduction of metric units in different areas.

When metric units became compulsory for pricing and weighing loose goods in 2000, there were no information programmes on radio and TV and very few leaflets distributed to help the public make the change. It is no wonder that many people thought the changes were made by stealth and that some market traders rebelled!

Other countries have shown that changing from imperial to metric can be straightforward. Most Commonwealth countries followed Britain’s lead on metrication and planned their own conversions. Countries such as Australia, New Zealand and South Africa changed over smoothly within a decade. Ireland completed its changeover to metric signage two weeks ago.

The Irish government has been replacing imperial distance signs with metric ones as they wear out – a low cost approach over the last decade. Their final step was to introduce metric speed limits. Very sensibly it planned to combine the switch with an improved safety campaign. Money invested in the scheme has paid for the metric conversion while providing real benefits to motorists at the same time.

Measure for measure: Irish officials with new metric speed signs

Britain, meanwhile, is stuck in an imperial time-warp. Our motor cars are designed with metric dimensions, our roads, signs and markings are metric. Yet metric units remain largely forbidden on the signs themselves.

The Department of Transport claims that metric signage could be confusing for motorists who lack a metric education; but do people really need to go to school to learn that there are 1 000 metres in a kilometre?

Ironically, millions of older imperial-educated motorists have happily driven on holiday on the Continent, in Australia, Asia or Africa and there are no reports of mass confusion with kilometres!

Indeed with ever increasing cross-Channel traffic, Britain’s isolation on units means that more and more journeys require mixing (and confusing) imperial and metric. With the changeover in Ireland this month we now have a land border with a metric country for the first time.

The Government has a national changeover plan to adopt the Euro even though no decision has been taken to proceed. Yet despite the fact that Britain is obliged to set a date to adopt metric road signage, there is no changeover plan! In this vacuum the costs of changeover may be increased by bad planning.

Ireland is not losing its heritage and culture by adopting metric speed limits and signs. Britain would not either. It is time that we followed Australia, New Zealand and now Ireland and modernise our measurement.

Modern Britain needs modern metric units – we should stop being sentimental about units from a bygone imperial era.