By Nick Assinder
Political correspondent, BBC News website
The minute Michael Howard believed he had been lied to by Boris Johnson, the Henley MP's fate was sealed.
Mr Johnson still has a television career
It is one thing having allegations about your private life splashed all over tabloid newspapers - and that, in itself, might well have been enough to finish Mr Johnson off.
But it is quite another to lie to your leader when the stories break. So many in the Tory party believe Mr Howard had no alternative but to sack Mr Johnson.
There had long been gossip in Westminster about Mr Johnson's private life - to the point where Tory bosses were beginning to get nervous.
The last thing Mr Howard wants in the run up to the next general election is any reminder of the sleaze rows that erupted around John Major and did so much to harm the party in the 1990s.
The Tory leader has promised to deal swiftly and decisively with any MP who threatens to damage the Tories' image and has previously acted over racist remarks made by backbencher Ann Winterton, for example.
On that basis alone, Mr Johnson was in trouble with his leader. He may have survived that, but the denials put the cap on it.
There are some in the Tory party who believe this was an accident waiting to happen - that controversy was the inevitable downside to Mr Johnson's colourful character.
Many of them, however, believed it was his editorship of the right-wing Spectator magazine that was most likely to cause problems for the party.
This need not be the end of his political ambitions
That was graphically illustrated by the recent article accusing Liverpudlians of wallowing in grief in the wake of Ken Bigley's murder.
Others, however, believe that Mr Johnson is a talented and attractive politician of just the sort the Tories need at the moment.
After the party conference in the autumn there were even those who started talking of him as a future leader.
It is certainly the case that the Tory frontbench will be a less colourful place without him.
And his sacking will inevitably reopen the debate about just how far an individual's private life should bear on their political life.
It is also the case that this need not be the end of his political ambitions. There are examples in all parties of MPs who have suffered similar setbacks only to stage comebacks or continue with successful political careers.
And, if Mr Johnson wishes to do so, there is no reason he should not follow them.