Fallon's 'painful' decision to resign

"What might have been acceptable 15, 10 years ago is clearly not acceptable now," Sir Michael Fallon told me tonight as he quit the government.

Clear to him now, and his departure will make clear to any other politicians in Westminster that behaviour they might have laughed off or treated as part and parcel of the rumbustious life is not acceptable and is not, it seems, acceptable to Number 10.

It has plainly for him been a very painful discovery to make.

Sources close to him don't believe that he is some kind of predator.

He has been known as a reliable minister, but also a sociable and approachable politician.

While sources close to him want to underline that they had not been told of any more allegations to come, or anything more serious, they were clearly aware that there could be more to come.

He did not feel that he could necessarily account for every event, every encounter in a long ministerial career without being able to guarantee that no more would emerge.

But it's also been suggested to the BBC that Number 10 was approached directly by several women with concerns about Sir Michael just this afternoon.

And within hours he had therefore taken the decision to go.

Number 10 won't deny or confirm what led to the resignation - they won't engage at all in any discussion of the whys and wherefores of the decision making process.

And as above, Sir Michael's team say they know of nothing else that was about to break.

But some Tory MPs are looking to what happened as potential evidence that when the prime minister said that she would take this harassment scandal seriously, she really meant it.

P.S. It also leaves Mrs May with a huge headache about reshaping her Cabinet at a time of political weakness. More of that tomorrow.