Taxi for Esther McVey? The Times’ Sam Coates has got hold of a remarkable letter from the head of the National Audit Office, Amyas Morse, to McVey, in which he accuses her of misleading MPs in her statements about the troubled Universal Credit programme.

Compounding the offence, he notes that he had already written to her privately before her second statement to MPs on the issue. It puts McVey in breach of the ministerial code and is, at the least, equal to the offence that led to Amber Rudd’s resignation. (It is arguably several degrees worse if McVey did in fact see the first letter from Morse, which would mean that she had knowingly misled the House of Commons rather than misled MPs through incompetence as Rudd did.)

But there are reasons to believe that McVey will stay where she is. May will be reluctant to remove a Brexiteer at a time when she looks likely to disappoint pro-Leave MPs. On the backbenches, McVey could potentially be a difficult rebel.

If McVey does remain in place however, it has troubling implications for British political norms and accountability in government. The NAO is a non-partisan body whose job is to scrutinise government departments – if an open letter of this type has no political repercussions for the minister involved it raises the question of what, if any, point there is in its existence and exposes a serious flaw in the British constitution. The second is that the norm that misleading the House of Commons is a resigning matter, already in bad nick after David Davis may well have done the same, will be further eroded.

And that’s one of the most troubling and unwritten consequences of May’s political weakness: that the political norms that keep governments accountable are under growing strain.