When Gordon Brown raised National Insurance in 2002 to put more money into the health service, it was seen as a huge political gamble. The Tories — including one Boris Johnson — denounced the move in furious terms.

In a sign of how far to the left the country has moved, the Tories are planning to do something very similar to cover the cost of a social care cap and dealing with the NHS backlog. If the Tories do this, it will put Labour in a tricky position. How do they respond when a Tory government raises taxes to put more money into the NHS?

But there is a political, as well as an economic, danger to the Tories in such an approach. Ahead of the announcement in the autumn, what remains of the low-tax Tory right will mobilise against the proposal. Inevitably, more resources will start to be demanded to deal with the NHS backlog.

The irony of this policy is that the cap is not, in fact, the biggest problem with social care. The low regard in which the work is held — as evidenced by the poor pay and the emphasis on agency staff — is a more pressing problem. But the cap has taken on huge importance.

The NHS might be the nearest thing the British have to a national religion, but for the property-owning classes, the belief you should be able to pass on that asset is a close second. The potency of the aspiration that wealth should cascade down generations means that any threat to it must be dealt with. Johnson’s calculation is that preventing any risk to this ranks higher than a commitment to low taxes in the hearts and minds of Tory voters.

The calculation is likely to be correct in southern seats with high property prices. The social-care cap will be the most middle-class part of the welfare state.

Longer term, the bigger worry for the Tories should be how they stop the rise of an ever-bigger state. It is hard to believe that this will be the last tax rise to cover the costs of social care and the ballooning NHS bill.