The defence budget is in deeper trouble than at any time since Labour came to power. But so are the general public finances, so the Treasury will not come to the rescue. In such situations, squeeze-and-postpone never suffices. Nettles have to be grasped – the sooner, the better.

Ministers must surely take a hard look at large programmes where costs are not yet too far committed. There may well be several of these. But one that stands out is the plan for two big aircraft carriers to deploy joint Royal Navy and Royal Air Force combat aircraft. If the case for these has been rigorously tested in Whitehall, little has emerged to outside view. The Commons defence committee, though keenly interested in the procurement arrangements, has scarcely attempted deeper scrutiny. There has been no public debate as there was over the Trident force.