What's next for Scottish Politics after Humza Yousaf resigns?

If politics is real life drama, and it was today, then who better than Shakespeare to draw on to describe the departure of Humza Yousaf as First Minister.

In the 'Scottish play', as superstitious actors like to call it, Malcolm says of the execution of the traitorous Thane of Cawdor, "Nothing in his life became him like the leaving it".

Now Humza Yousaf is very much alive, physically, but life at the top of Scottish politics is definitely over. He is soon to leave it.

And his speech this afternoon at Bute House, the official residence in Edinburgh that he is soon to move out of, had a Shakespearean quality.He told the assembled journalists: "Politics can be a brutal business. It takes its toll on your physical and mental health. Your family suffer alongside you."

At times emotional, Mr Yousaf also tried to put into context what he told me when I interviewed him about a month ago to mark his anniversary as First Minister. At the time he talked of the "honour and privilege" of serving.

Today he put it this way: "I cannot tell you what an honour it is being the First Minister of the country I love, the country I am raising my family in, and the only country I will ever call home."

That he was sincere was not in doubt, that he had regrets was obvious, and that he took responsibility for his own demise was inevitable.

At the heart of him being forced to stand down (and he was forced) was his decision to end the Bute House agreement to govern Scotland with the Scottish Greens in a 'power sharing agreement', a coalition in all but name.

He unceremoniously sacked the Greens last Thursday because he thought it was the only way to end the tensions over the alliance inside his SNP group, and between the parties.

"Bonds of trust"

To use Mr Yousaf's word today, it was "brutal" and Patrick Harvie and Lorna Slater, the Greens co-leaders were absolutely furious when they suddenly became ex-ministers.

The electorate had been 'betrayed', Slater said. The "bonds of trust" between the parties broken. Humza Yousaf 'could not longer be trusted'. One act of political brutality begat another.

Today Yosaf admitted: 'Unfortunately, in ending the Bute House Agreement in the manner that I did, I clearly underestimated the level of hurt and upset that I caused Green colleagues.'

You can say that again, First Minister. And he did, in a slightly different way, adding: 'For a minority government to be able to govern effectively, trust when working with the opposition is clearly fundamental.'

And that was the problem. On Thursday he called his move 'leadership'. By last night when it became clear that with the Greens against him, he would lose a vote of confidence called this week in Holyrood, he had concluded "repairing our relationship across the political divide can only be done with someone else at the helm".

Who will be 'at the helm' is now crucial to thawing relations with the Greens, as they must do for legislation to pass at Holyrood, if the SNP do not want to rely on the Tories and Labour. And they don't.

Were it to be John Swinney, Nicola Sturgeon's former deputy First Minister, who is gaining substantial support from senior colleagues, that might happen.

It would be much, much more unlikely if it were Kate Forbes, the former finance secretary who came close to beating Mr Yousaf in the election to replace Sturgeon.

The Greens, and many in the SNP at Holyrood find Forbes' religion-based socially conservative views - on abortion and gay rights for example - unacceptable.

That did not, however, stop 47.9% of SNP members voting for her the last time, with Mr Yousaf winning 52.1%.

It is hard to see why they would not do so again, which explains the support from senior MSPs and MPs for Swinney, increasingly seen as the 'stop Forbes' candidate.

As this blog is being written, we do not know if Forbes will stand. She has a very, very big call to make.

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In that passage from the Scottish play, the quote from Malcolm comes after the King has asked Is execution done on Cawdor? Are notThose in commission yet return'd?

Malcolm replies:My liege,They are not yet come back. But I have spokeWith one that saw him die; who did reportThat very frankly he confessed his treasons,Implor'd your Highness' pardon, and set forthA deep repentance. Nothing in his lifeBecame him like the leaving it.

Mr Yousaf has not committed treason, of course, but his statement did have a large element of confession about it. And he did, in effect seek repentance.

It was a dignified, self-aware and very human speech but it was an admission that he had made a huge political mistake. A mistake that has cost him the job he valued above all else. And potentially cost his party by bringing to an end its long, and extraordinary, dominance of Scottish politics.

Nothing in Humza Yousaf's political life became him like the leaving of it.