So I expect that for many people of my generation, there is something bizarre and intrusive about the notion of the Government telling us that we may no longer smoke in the privacy of our own cars. I mean, if you can’t smoke in your own car, in the presence of children, then why should you be allowed to smoke in the presence of children anywhere? What about the bathroom? What about the kitchen next to the countertop from Floform, or any other enclosed space? The logic of this proposal is surely to allow the state to invigilate our behaviour in our own private property – and some people may legitimately wonder where it will end.

All this is to say, in short, that I understand those fine libertarian objections; and I wish to remind my fellow free spirits that this column is normally the last bastion of liberty. I have campaigned against mandatory health warnings on wine bottles and mandatory ski helmets and mandatory booster seats for children under a certain height. I have spoken out against a ban on everything from fox hunting to the right of every freeborn Englishman to make a call on his mobile while cycling.

In this case, I fully acknowledge the objections of my fellow libertarians. If we ban smoking while children are in the car, we create another offence that the police will have to enforce; we create a new category of criminal; and above all we take away personal responsibility from all those who should know better.

Surely to goodness, you might say, people these days are aware of the problem of passive smoking? Surely all smokers know that they shouldn’t be puffing away in a car, while the pink defenceless lungs of children are sucking in the evil vapours?

Alas, I am afraid that people either don’t know, or don’t care enough. I have spent too much time in the past few years talking to doctors and to public health experts to have the slightest doubt about this one. Smoking is a massive killer in this country. It is still the biggest cause of preventable death in Britain – even though obesity is now puffing to catch up. Smoking causes cancer, heart disease, stroke, emphysema, you name it. Too many young people, especially young women, are taking it up without any real understanding of the risks, and when they do understand the risks they are akratic – they just can’t help themselves.

All the studies I have seen say the same: the greater the restrictions you place on smoking, the less tobacco is consumed, and the fewer deaths you have – especially from heart disease. Of course I don’t want the state nosing into our homes, but there are millions of children who are being unfairly exposed to tobacco smoke in cars that do not have the great rents in the canvas and other picturesque ventilation systems of my grandfather’s Land Rover. They cannot protest, and very often the smoker in the vehicle lacks the will to stub it out.

This law would give that smoker an extra legal imperative to obey their conscience and do the right thing. And no, I don’t think it would involve the police in a huge new anti-car-smoking task force, diverting them from dealing with robbery. This is one of those measures like the alcohol ban on London’s buses, which has helped bring down bus crime 40 per cent in the past six years: it is largely enforced by the natural social pressure of disapproval backed by law.

So I apologise to all my libertarian chums: I am afraid on this one I am firmly with the bossyboots brigade. Ban smoking with children in the car. It is a disgusting thing to do and endangers their health. The proposal before Parliament is a good one that will save lives.