Just how defensive is the defence sector? BAE Systems and others involved in the Eurofighter project are in a rearguard action against possible cancellation by the UK government of the third production run of the jets. Meanwhile, Babcock claims to be winning even more contracts.

But what appears to be a paradox is in fact consistent. Defence budgets are certainly hard to cut. Big projects are a bit like the aircraft carriers BAE and Babcock help build: hard to turn round and difficult to stop in a hurry. But defence requirements are changing as military threats change. That makes some of the largest projects vulnerable to penny-pinching by politicians, who suddenly develop a razor-sharp focus on the utility of big contracts, such as Eurofighter.