The most remarkable thing about the ban on smoking in cars when children are present, which will pass the Commons later today, is how quickly minds have changed. There’ll be ministers and MPs voting for it today who were dismissing it as absurd nanny-statism just a week ago.

What has happened is that MPs, particularly Tory and Lib Dem ones who have a genuinely free vote on the matter, have reflected on how far the state already restricts liberty when it comes to smoking. Once you have decided to ban smoking in pubs, where adults go voluntarily, and even private members clubs, then it is very hard to defend allowing people to smoke in a confined space when a child is present. Indeed, as David Willetts argues given that passive smoking does do harm and children are not free to choose whether to travel in a car with an adult who is smoking, the ban is justified on philosophical terms.

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Even those such as the Justice Secretary Chris Grayling who will vote against the ban are doing so reluctantly. Grayling fears that the ban is close to unenforceable and so should not become law.

Some sceptics of the ban wonder where it will all end. But I think there is a difference between legislating to stop harm and legislating to make people do things, like feeding their child healthy food. I would, though, not be surprised—given the rate of change—if smoking in a room where children are present becomes illegal before 2025.

Tags: Children, Chris Grayling, David Willetts, Smoking