The 39-year-old, now pregnant with her first child, was sent into a “tailspin” at the age of 17 by the suicide of a local boy, which prompted her to cut herself, drink “far, far, too much” and become “belligerent and angry”.

Ruth Davidson praised after she reveals mental health struggles

A year later she was diagnosed with clinical depression and started having “desperate, dark, terrible dreams” and suicidal thoughts. Her depression was “like a smothering black blanket over my head cutting out the sky.” Ms Davidson says she is “still frightened” about going back to the “psychological place I once inhabited”, values her relationship and mental health too much to move south and relies on “structure, exercise, forward momentum, measurable outcomes” to combat anxiety.

Ruth Davidson. Leader of the Scottish Conservatives, Ruth Davidson.

Asked about becoming a peer or MP to advance her political career, Ms Davidson said such speculation was “bollocks.”

It’s a lot to take in. Ruth Davidson’s jaunty, confident manner has always been her strongest calling card. Indeed, in a front page Sunday paper interview, the Scottish Tory leader is pictured heavily pregnant, side on and winking. It’s a typically bold, direct gaze that makes it hard to imagine any earlier moments of depression, anxiety and distress. Of course, that’s why Ms Davidson’s story is so powerful – it shows that absolutely anyone can experience mental health problems and recover sufficiently to apparently revel in the vicious world of party politics.

Actually, in the “me too” era, Ms Davidson’s admission of vulnerability is a demonstration of strength. The same is true of Nicola Sturgeon who admitted last week that she was bullied at school.

Speaking at a special First Minister’s questions for Scotland’s Year of Young People, the SNP leader said: “I went through periods at school of bullying. I wouldn’t say it ever got to a really serious level that made me scared to go to school. But I had experiences at primary school where it certainly was sufficient to involve a teacher.”

This has done Ms Sturgeon no harm. At a time when respect for the distant, lofty, superior political class is waning, there’s little to lose from appearing more like the electorate and less like indestructible political automatons. Confident women in top positions can make such moves – last week at Westminster Lib Dem deputy leader Jo Swinson cradled her baby on Parliament’s famous green benches for the first time during a Commons debate.

But the most significant aspect of Ruth Davidson’s revelations has hardly been discussed. Southern commentators insist she has prioritised personal life over career, but that may not be true. In choosing Scotland over England, Holyrood over Westminster and the chance of becoming First Minister over Prime Minister, Ruth Davidson has really made a very bold career move. She has nailed her colours unequivocally to the Scottish mast, and for Scots – even prospective Tory voters – such an explicit declaration of loyalty to this country is a vital prerequisite to being taken seriously as a political leader at Holyrood.

Currently, Ruth Davidson has support in all the wrong places. Her farewell to Westminster topped the BBC1 Andrew Marr programme on Sunday but was not covered by Sunday Politics Scotland. That might simply be down to superior staffing levels which facilitate last minute changes, but the omission of Ruth Davidson from BBC Scotland’s only TV current affairs programme says a lot about her relative popularity. It’s sky-high south of the Border – fair to middling here.

The inconvenient truth is that her star waxes with independence on the agenda because she unquestionably looks like the toughest unionist in town. But when politics focuses on the day job, it wanes.

BBC Good Morning Scotland presenter Gary Robertson recently tweeted: “We’ve had a longstanding request for an interview [with Ruth Davidson] over recent weeks. The Scottish Conservatives say she will be available at the Tory party conference.” Adam Morris, the Scottish Conservatives’ head of media accused Robertson of “pandering to deranged cybernats.” GMS editor Allan Price replied; ““Absolute piffle. It’s all about transparency with the audience, nothing more.”

Quite apart from the democratic and economic outrage of Brexit, Scots have been roundly disgusted by the Tory benefits regime; punitive sanctions, catastrophic universal credit, bedroom tax and the heartless decision to remove mobility cars from disabled people.

Until Ruth Davidson cuts the link with the UK Tories, she will always be leading the nasty party in Scotland. As it is, her welcome and frank admission of mental health problems makes it all the more extraordinary that she could watch her own party inflict stress and misery for eight long years on the unemployed, disabled and chronically ill. Debt and poor-quality jobs are the most common triggers for mental illness. Yet under her party’s watch, these problems have soared.

As one doctor observed on twitter; “I’ll remember [Ruth Davidson’s mental health revelations] next time a patient has their benefits removed as a consequence of her party’s policies.”

So, never mind the forthcoming autobiography. If the Scottish Tory leader wants to make her life in Scotland not London, that’s welcome. But disowning a long legacy of Tory cruelty is the thistle she must really grasp.

Lesley Riddoch: Ruth Davidson brave in mental health revelations but '˜must now differ from UK Tories'