I know that the reasons given for tax increases are usually lies – the only reason is to boost government coffers – but the supposed environmental reasons for increasing car tax really bug me. I’ve got a knackered old Saab which is seven years old and therefore comes under the new regime, so from next year I’ll have to shell out a fifth of its value in car tax every year. Come to think of it, it’ll be more than a fifth because by next year it’ll be worth approximately 2p and the annual tax will be £300.

Given that the kind of car I need doesn’t change – I can’t fit a baby, a pram and a dog in a Smart – and that the tax is painful, that gives me two options. I can get an older estate car, or I can buy a newer estate car.

Older isn’t that green, because older cars pollute more. If I go back one  year and buy an identical Saab, the petrol and the diesel versions both pump out more CO2 than my current car, because the engines were revised to make them less polluting in 2001. Other manufacturers aren’t any better. An eight-year-old Mondeo estate pumps out more CO2 than my seven-year-old Saab whether I go for the petrol or the diesel. And of course, as cars get older they become dirtier.

Newer isn’t very green either, because most of a car’s environmental impact is in its manufacture. So changing a car that’s running more or less okay in favour of a newer one is just wasteful, and kills polar bears.

Which leaves a third option: keep the car, pay the tax, and don’t change anything.

Only a cynic would suggest that that’s exactly what the government expects most of us to do…