After a week that has seen Nick Clegg threaten to dismantle  most of Andrew Lansley's key NHS reforms – without a hint of dissent from David Cameron – it's not surprising that the Health Secretary's patience is wearing thin.
Four months ago, Clegg, like almost every other Liberal Democrat MP, voted in favour  of the Health and Social Care Bill at its second reading. Yet he now insists that the NHS will not be open to any "any qualified provider" and that the reforms must promote co-operation, rather than competition.
Today's Daily Mail reports that Lansley has told Cameron to "back me or sack me" , in a final attempt to persuade the PM to come to his aid. The Health Secretary came close to issuing such an ultimatum in public when he declared: "I don't want to do any other cabinet job. I'm someone who cares about the NHS who happens to be a politician, not the other way around."
Lansley's threat prompts the question: at what point would he walk away? He has already accepted that Monitor, the health regulator, will not be used to enforce competition and that GP-led consortiums will now include nurses and local officials on their commissioning boards. But he is less likely to accept the abandonment of the "any qualified provider" clause – one of the defining features of his proposals.
The key question remains whether Cameron shares Clegg's objections to the reforms, or whether his deputy is merely freelancing. It is hard to see how Cameron could accept Clegg's demands without precipitating Lansley's departure and further antagonising his increasingly restive  backbenchers.