Ruth Davidson is off to spend more time with her family, and Scottish Unionism has lost its top gun.

Rarely has a political movement owed so much to one personality. No-one seriously believes the Scottish Conservatives’ recent revival could have been possible without the working-class, kick-boxing lesbian “fae the Kingdom of Fife”.

Davidson breathed life into the moribund Tory party by confounding expectations. She was an exercise in confusion marketing; the antithesis of the reactionary, middle-class, middle-aged, strait-laced Scottish Tory image. She talked straight, and she sometimes talked dirty.

Her LGBT liberalism finally rescued Unionism from the old Rangers-supporting, Union Flag-waving, sectarian taint that dated from the days when the Scottish Conservative and Unionist Party really was the Orange party.

This rebranding took the Tories from the margins of politics to the main opposition in Holyrood in only three years.

She then won 13 Westminster seats at the 2017 General Election, more than the Democratic Unionist Party, Theresa May’s coalition partners. The likely loss of those Scottish seats at the next General Election could be crucial to the fate of the United Kingdom. It may not survive her.

For First Minister Nicola Sturgeon, the loss of her most dangerous foe caps her best-ever summer.

Last month, the Labour shadow chancellor, John McDonnell, came north to the Edinburgh Festival and, in a remarkable reversal of policy, announced that Labour would not stand in the way of another Scottish independence referendum. Scottish Labour’s leader, Richard Leonard, doesn’t seem to have quite got the message.

Boris Johnson’s election as Conservative leader and Prime Minister (unelected) was an even greater political windfall for Sturgeon. Of all the potential candidates for Number 10, the Bullingdon English nationalist was the best because he was the worst. The Tories haven’t had a leader so out of tune with Scottish sympathies since Margaret Thatcher. His very voice seems redolent of English public school elitism.

Now, Johnson’s reckless pursuit of a no-deal Brexit has served to remind Scots just why they voted overwhelmingly to Remain. In this week’s Herald readers’ survey, support for Brexit is now down to 16%. Some 38% of Scots voted to leave the EU in the 2016 referendum.

His decision to prorogue Parliament allowed Sturgeon to announce that it was a “dark day for democracy” and accuse him of exercising dictatorial powers. As Scotland is dragged kicking and screaming out of the Europe, power is being centralised in Westminster as never before. This has renewed the debate about the powers of the Scottish Parliament. If the PM is prepared to run roughshod over Westminster, how is he going to treat Holyrood in future?

Davidson’s departure comes not a moment too soon for the First Minister. There has been grumbling among SNP activists on social media about the lack of progress to the next independence referendum. No-one believes that Johnson will agree to one, which makes Sturgeon’s promise of a referendum in the second half of 2020 sound vacuous.

Why wait, said the former SNP MP George Kerevan. She should withdraw MPs from Westminster, he tweeted, and “declare an independence referendum immediately REGARDLESS of London’s permission”.

He added that Gandhi and Mandela “didn’t await permission to free themselves”. Many thousands of independence supporters stand ready this weekend to join a campaign of civil disobedience in support of self-government. All Sturgeon needs to do is give the word, and they would be manning, and womanning, the barricades.

But I don’t think the First Minister is going to go down an extra-parliamentary, unconstitutional route to independence. Recalling Holyrood is a possibility, though it would have to be for a specific purpose, not a unilateral declaration of independence. She certainly won’t call an unlawful Catalan-style unauthorised referendum. Nor will she withdraw MPs from Westminster. She is not a risk-taking, insurgent leader.

This doesn’t mean Nicola Sturgeon has given up on independence, or that the Union is saved. On the contrary, the events of the past week may have destroyed the last vestiges of support for the Union in Scotland, and made some form of constitutional divorce inevitable. But Sturgeon is a cautious lawyer. She is unlikely even to request a referendum unless there is a significant increase in support for independence in the opinion polls.

Support for Yes is certainly edging up over 50% in some polls – but it is painfully slow. Most Scots tell pollsters that they expect Scotland to be independent some time in the future, but that doesn’t translate into a demand for a referendum today. The landscape of Brexit is just too confused. We can’t even be sure when or how, or even if, the UK is leaving the European Union.

The First Minister is a gradualist, and her sights will be set, first of all, on the next General Election. She wants those 21 seats that she lost in 2017 – that really hurt. Then there is the possibility of a hung parliament and working in some form of confidence-and-supply arrangement with Labour. Now that there is agreement on indyref2, a Corbyn coalition is eminently doable.

If there is no General Election, or if the Tories win again, she will concentrate, I believe, on obliterating the Tories in Scotland in 2021. She has really hated them being the main opposition party in Scotland and no doubt feels a personal sense of responsibility to see them back in their box. With Richard Leonard in difficulty, there is now no effective opposition to the SNP in Holyrood.

She will put indyref2 high on the agenda for the 2021 Scottish elections, and use that as a lever to get a Section 30 from Westminster for a legally binding referendum, perhaps in 2023/24, 10 years after the first independence referendum. That may seem a long way off for her more ardent troops, but in the great scheme of things it is a blink of an aye.

There is speculation that she might not lead that independence campaign. A number of nationalist insiders believe the First Minister could resign following revelations in the forthcoming Alex Salmond court case. But I think it unlikely that Sturgeon will be going off to spend more time with her family any time soon.

There’s just too much going on. Her number one enemy is gone, Johnson is staying and there is Brexit chaos all round. The SNP is riding high in the polls fully 12 years since the party came to office. What more could any leader wish for? Family can wait.