The UK cannot afford a cold war with the US. And the ambassador had a duty to resign from the moment he became a liability instead of an asset for the country. No one had to even tell him to do so, it was his duty. The whole purpose of an ambassador is to facilitate diplomatic relations, not to poison them. That he hung around a couple of days and forced politicians in the UK to take position on the issue was his failure. He was guilty of being an incompetent buffon. Whatever Trump's problems, the guy is nowhere near having his administration collapse. Predictions that will happen have been made from the very start and he's still there. It looks to me very likely that he'll will the next election. The ambassador's evaluation of the situation in Washington was worse that useless, it was wrong and a liability to the UK.