Humza Yousaf's extraordinary miscalculation will go down in Holyrood history

The First Minister was visibly emotional as he announced his resignation

“Politics can be a brutal business,” said Humza Yousaf, just moments before his voice cracked with emotion as he paid tribute to his wife and children. “It takes its toll on your physical and mental health. Your family suffer alongside you.”

The last few days had exacted a heavy price. The First Minister’s decision to scrap the Bute House Agreement – and the manner in which he did so – was an extraordinary miscalculation that will go down in Holyrood history. It was a gamble he lost in spectacular fashion.

In his resignation speech, Mr Yousaf admitted he had “clearly underestimated the level of hurt and upset” it would cause within the Green Party. Insiders said he first realised he was in trouble late on Thursday afternoon, when the Greens said they would back a motion of no confidence tabled by the Conservatives.

First Minister Humza Yousaf arrives at Bute House ahead of a press conference. Picture: Andy Buchanan/AFP via Getty Images

Mr Yousaf expected “turbulent times” as he sought to govern as a minority administration. However, he had not anticipated this. As Friday became Saturday and the Greens’ position did not shift, the First Minister began to see the writing on the wall.

At 12.30pm on Sunday, Mr Yousaf and his closest advisers met in the drawing room of Bute House, his official residence in Edinburgh. Over the next few hours, they talked through his options, or lack of them. A source said there was a “pretty strong consensus” that a deal with Alex Salmond’s Alba Party was a non-starter.

By the end of the meeting, Mr Yousaf had pretty much made up his mind. His decision was set in stone the following morning. Just a few hours later, he was announcing his resignation in that very same drawing room to a gathered throng of journalists.

The support of Ash Regan, Alba’s sole MSP, would have been enough to get Mr Yousaf over the line. But it would not have provided him with the majority necessary to pass legislation, and some within the SNP would have found it difficult to stomach, to put it mildly.

Humza Yousaf

“Alex obviously loving all this attention this morning, as he should, with his party having never had anybody elected to anything,” tweeted long-serving SNP MP Pete Wishart on Sunday. “He now wants to exert influence over our Government and he must be told quite clearly that can never, ever, happen.”

Mr Salmond’s talk of a potential electoral pact between the two parties was met with horror from some SNP parliamentarians. Stewart McDonald, the MP for Glasgow South, said it would “go down like a bucket of cold sick with voters”.

During his speech, Mr Yousaf said a route forward was “absolutely possible", but added: “I am not willing to trade my values and principles or do deals with whoever simply for retaining power.”

Mr Salmond later claimed the First Minister was still trying to do a deal with Alba at 7.30am on Monday, but the SNP’s “old guard” had blocked it. A source close to Mr Yousaf dismissed this as a “simple lie”. The First Minister did speak to Ms Regan, they said, but only to tell her it wasn’t happening.

Mr Yousaf is said to be philosophical but regretful. He is well-liked by the team around him. “He is very, very good at personal relationships,” one said. “In his entire time as First Minister I don’t think I heard him shout once.”

But personal charm was not enough. In the end, he proved a poor judge of events. On Thursday, his spokesman told journalists the end of the power-sharing deal met with an enthusiastic reception at an emergency meeting of the Scottish Cabinet. Ministers apparently slapped the table in approval.

For the Greens, this sort of thing was only ever going to rub salt in the wound.

"I’m grateful for lots of things in life,” Mr Yousaf said in response to a question from a journalist as his political career fell apart on Friday. “I woke up this morning with my four-year-old, soon to be five, in my bed and was able to spend some time getting her ready for nursery this morning, to brush her hair, to get her changed, to get her ready to go.

"So I’m grateful for all the things in my life – family, friends. But also, I am genuinely grateful – not just grateful, it’s a huge honour for me to be the leader not just of my party, but of this country.”

It was a nice answer, and a reminder of the human being at the centre of the political storm. On Monday, in Bute House, he was visibly emotional as he spoke of his “absolute debt to my wonderful wife and beautiful children, and my wider family for putting up with me over the years”.

He added: “I’m afraid you’ll be seeing a lot more of me from now. You are truly everything to me.”

The SNP will now seek to elect its third leader in just over a year. John Swinney, the former deputy first minister, has already attracted strong support. But Kate Forbes – who narrowly lost out to Mr Yousaf last time – is also said to be giving it “serious consideration”.

Whoever emerges will have a tough job on their hands. Polls show a party struggling to regain the momentum it once took for granted. There are clear divisions about the best route forward. Meanwhile, Anas Sarwar, the Scottish Labour leader, has his eyes on the keys to Bute House.

Politics, as Mr Yousaf said, can be a brutal business. With a tricky election looming, it could be about to get even more bruising for the SNP.