Going the extra 1.60934 km

A few years ago we visited family in Australia, which was a great experience. Something you notice quite quickly there is that although you're driving on the left, speaking English, drinking tea and talking about cricket, something is different. All the road signs are metric. I understand that it took about 7 years to do most of it, with the final tidying up completed in the late 80s. The reason I remembered this was a line in a novel referring to something being 1km from a location in London. It's just not what you normally see.

Back here in the UK, everything I buy from the supermarket is packaged in metric quantities (except milk, unless you buy a litre), but recipes persist with ounces. I buy diesel by the litre, my car is rated at 109g of CO2 per km, but the road signs are in miles and it does 55 miles per gallon. If I buy beer in a bottle in a pub or a shop, it's usually in 250, 330 or 500ml bottles, but in a pub you buy draft beer by the pint (568ml).

My question is simply, why? What is it about pints, miles and gallons that means we have to have this messy left-over. I was learning about the metric system at primary school in the late 60s and throughout University had to use the SI system for all measurements. Why didn't we just go metric properly once and for all? Instead the old units linger. Even my kids use 2 systems.

No doubt full conversion would produce the usual anti-EU rhetoric from the more xenophobic parts of the press. Would it really rob us of our national identity to resolve the remaining issues? Not really - we have to use metric to trade with the rest of the world - it's just that market traders want to be free to sell pounds of bananas. It seems to me that the only credible objection to full conversion now would be the prohibitive cost, especially for roads and transport.

So stay calm, Britain, you can sleep peacefully in the security that you can carry on drinking beer by the pint, (as long as you don't drive any miles, burning gallons of petrol, immediately afterwards!)