The MoD said no decision had been taken but the site was being scrutinised, along with all defence expenditure, to secure "the best value for money".

BBC: An aircraft lands at RAF Northolt

Up to 40 separate studies of defence expenditure are close to completion, which will be submitted to the NSC's small secretariat, led by the new national security adviser, Sir Peter Ricketts, a former head of the Foreign Office.

ECONOMIST: The future of British defence

Details will come in his pre-budget report in November, but some expenditure has already been fast-tracked in housing and defence.

ECONOMIST: The politics of a shrinking economy