Theresa May has just days to seal her Brexit destiny

Theresa May is behaving like a prime minister who has worked out that taking cautious steps to cling on to power is a bankrupt strategy.

The ruthlessness with which she dispatched her defence secretary, Gavin Williamson, who was till recently her closest ally is one piece of supporting evidence.

The point is that when he allegedly told senior armed forces personnel that "I made her and I can break her", it was not just bluster. As behind-the-scenes organiser of her campaign to become leader (dispatched to do that job by Cameron and Osborne - who wanted to stop Boris) and as her ruthlessly effective chief whip, he was an invaluable supporter.

From which it follows that if Williamson now chooses to become her enemy, he would be formidable.

But she doesn't care.

Why not?

Well on her brief walking holiday, it may well have sunk home that she now has more enemies than friends on her own benches. And she may well have calculated that her only hope of earning an honourable place in history is to put what she sees as principle ahead of trying to placate colleagues who will never be placated.

Again there was more evidence of her liberation from the shackles of party fealty yesterday.

When she was interviewed in the afternoon by senior MPs - those who chair select committees - she treated Labour ones with courtesy while showing near contempt for those Tory Brexiters who have blocked her attempt to secure her own version of Brexit (compare how she answered questions posed by Labour's Hilary Benn with her response to the Conservative Sir Bernard Jenkin).

But perhaps most important is her replacement of Williamson with Rory Stewart - because Stewart will change the balance of opinion on Brexit in her cabinet in an important way.

Williamson became a born-again Brexiter over the past year or so, and argued the case for a no-deal Brexit with near religious fervour - and it matters not whether this was sincere or as positioning ahead of a looming leadership election.

By contrast, Stewart - as he said very powerfully on my show last night - believes with a passion that both no-Brexit and a no-deal Brexit are toxic and unacceptable; he would accept any form of managed, agreed Brexit that (to the greatest extent possible) puts the issue behind the government and all of us.

I was gobsmacked (really) when he did not demur in the slightest when I put to him that the chief whip had told cabinet on Tuesday the only way to get a deal through the house of commons would be for the PM to agree either to Labour's demand for a customs union or to tag a referendum on to any deal as a confirmatory mechanism.

In fact, he said he enthusiastically supported "reaching out across the aisle" in that way. And if a pact with Labour that breached the PM's erstwhile red lines were to secure a stable majority to pass all the necessary Brexit legislation over the coming weeks, he would be prepared to pay the price of seeing some of his ERG Brexit colleagues quit his party in disgust.

"That is a risk" he said. But "doing Brexit cross-party could turn out to be a smart thing to do, to reassure investors for example that this thing will last".

So the prime minister now has around her a powerful caucus of ministers - Hammond, Rudd, Gauke, Lidington, Rudd, Clark, Mundell, Gove, Stewart - who are urging her to put country before party, and agree a deal with Jeremy Corbyn that perhaps a majority of her own MPs would hate.

What's the worst that could happen?

Well there are three failure scenarios, all of which could almost simultaneously happen.

1) She could call Corbyn's bluff and in the end find out that he has been negotiating in bad faith; it may turn out that he simply could not bring himself to do a deal with any Tory prime minister. But that would probably reflect worse on him than her.

2) She could so enrage her party that they find a way to throw her out double quick. But she knows that's going to happen in pretty short order any way. So in that sense she has literally nothing to lose from doing what she thinks is the right thing by the country.

3) She could so alienate her Brexiter MPs and Northern Ireland's DUP, whose support is vital to the Tories remaining in office, that they would join forces with Labour to force a general election. But May knows that the parliamentary arithmetic may make it impossible to secure any kind of Brexit ahead of an election in any case. So again she would have lost nothing if an election was precipitated.

Or to put it another way, even though the prospect of Theresa May securing a pact with Labour for a managed departure from the EU is a remote one, trying and failing is not such a terrible thing for her - because she knows that whatever happens, her time in 10 Downing Street is almost up.

Her destiny is sealed. Her time as prime minister is drawing to a close. So why wouldn't she boldly go where she has never gone before, and seek a genuine Brexit alliance with her implacable opponent, Jeremy Corbyn?