Everyone understands the need to leave on a high - whether it’s Prime Ministerial legacy or a sense of completing the job.
But the new defence investment plan that Starmer's signed off leaves Burnham with an unexploded bomb in the shape of a five billion pound debt.
Does Burnham stick to the plan? Or does he rip it up? And how does he fill the hole if he goes along with it?
We ask TUC secretary general Paul Nowak what unions want from a Burnham premiership.
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