Andy Burnham, the man widely expected to become prime minister on 20 July, has been handed a lovely parting gift by outgoing PM Sir Keir Starmer: a £4.7bn gap in the defence budget. Defence minister Luke Pollard cheerfully informed the BBC that the next chancellor - who, by the way, hasn't been named yet - will need to "find the resources" in the autumn Budget. Because nothing says 'smooth transition' like a multi-billion-pound IOU.

Sir Keir, in one of his final acts as PM, announced a £15bn defence investment plan (DIP) over four years to reverse the "corrosive hollowing out" of the armed forces under the Conservatives. The Treasury, however, has only identified £10.3bn in savings, leaving a tidy £4.7bn shortfall for Burnham to plug. Pollard made it clear this is "pretty standard fare" - governments love making announcements and leaving the details for the next budget. It's a time-honoured tradition, really.

The outgoing PM ruled out borrowing to fund the increase, so the money will be squeezed from other departments: the Department for Transport is slashing £700m from roads projects (the A38 Derby Junctions and A46 Newark Bypass are on the chopping block), and the Department for Energy Security and Net Zero is coughing up an extra £2bn. More detailed plans are promised for autumn - because vague promises are always reassuring.

Burnham, who was only told about the funding gap on Tuesday, has yet to comment on where he'll find the extra cash. One ally described it as "another spending pressure," which is a polite way of saying 'this is a massive headache.' Defence Secretary Dan Jarvis said there will need to be "conversations" with the next PM, but insisted it's "not unreasonable" to sort this out at a major fiscal event. Because what could be more reasonable than a looming £4.7bn hole?