The trouble with governments is that they are always telling us what and what not to do for our own good.

A few years ago, it was: drive diesel because that will save the planet. If they had paused a moment and possibly asked Autocar, we could have told them that never mind about a naturally occurring gas coming from petrol cars, diesels are rather more evil.

Read more: government plans diesel scrappage scheme

Well, for the short-termist, quick-fix politician, it is now time to think of another clever wheeze to get people out of their rotten old diesels and into something much newer. Hence the proposed schemes.

Scrappage ones are meant to be stick with a side order of carrot. You give up a perfectly serviceable vehicle for a discount on something much newer. It sounds like a good deal.

The trouble is that on environmental grounds, such a scheme is the worst of all worlds. When it comes to using the earth’s resources, making a car from scratch tops the lot. Which begs the question, surely an engineer can come up with an exhaust based fix to make them better. However, it is too late for that.