It has been another one of those difficult weeks for Nicola Sturgeon. Another man she thought she knew well turns out to have been beyond the pale.

He is presently behind bars and expected to remain there for many months, perhaps years. The crook in question is Peter Murrell, the man she married.

Naturally it was a shock to the Sturgeon system. She ‘loved’ and ‘trusted’ him – not to mention lived with him for 20 years while having ‘no knowledge or suspicion’ that, for much of that time, he was pilfering funds from the party she led to feather their nest.

‘I am utterly appalled that he did so and cannot begin to understand why,’ she said in a statement. She feels ‘hurt’, ‘let down’, ‘deceived’. It is a ‘profound personal trauma’.

Many will note an eerie familiarity to the wound-licking here – and, indeed, to the circumstances which gave rise to it: The former First Minister Nicola discovering to her apparent bewilderment that someone close to her was not who she thought he was.

A few years ago, it was her mentor and closest political ally Alex Salmond who, it turned out, she had read all wrong.

He was her ‘bestie’ and she knew him better than anyone, she used to boast, with the possible exception of his wife Moira.

The scales fell from her eyes in the dining room of her home in 2018 as Mr Salmond handed her a Scottish Government letter informing him he faced sexual harassment allegations.

What was worse, the man she had idolised admitted one of them was substantially accurate. ‘I felt sick,’ Ms Sturgeon wrote later. That meeting ‘knocked me for six’.

Two years later, there were devastating revelations on the true nature of another member of her inner circle. This time they involved finance secretary Derek MacKay – a friend as well as a colleague – who was tipped to replace his boss in Bute House one day.

But, as he was being groomed for the First Minister’s job, he in turn was grooming a 16-year-old boy. She thought he was a rising star; he was really a predator.

The teenager’s parents had contacted the Press and transcripts of the damning private messages the politician had sent him were about to be published.

In her autobiography, Frankly, published last year, Ms Sturgeon recalled: ‘I went into a bit of denial initially, thinking it couldn’t possibly be true. Could it?’

Every word was true. And Ms Sturgeon’s reaction? ‘I felt sick…’

‘The feelings of shock and upset were palpable.’

And yet, she admitted last year: ‘I still count him as a friend.’

Whatever Alex Salmond’s indiscretions – and it must be remembered the late former First Minister was cleared of all the criminal charges after a string of women accused him of sexual harassment and assaults – they were not Ms Sturgeon’s misdeeds.

Similarly MacKay’s grotesque bid to seduce a schoolboy was not on her. He dug his own political grave and, rightly, remains in it.

But, in Ms Sturgeon’s place, might any self-aware politician be driven to wonder this week why this keeps happening to them? Why do key people in her life turn out not to be the men she supposed at all?

Her mentor was a handsy ladies’ man given to inappropriate behaviour towards women who were not his wife.

The Press knew it – indeed several female journalists found themselves on the wrong end of it – even if the politician who ‘knew him best’ was seemingly oblivious.

Her estranged husband, we now know, was engaged in criminality for most of their marriage. As SNP chief executive, he siphoned off more than £400,000 of party funds to spend on luxury items, many of them outrageous in their extravagance. A fountain pen costing £4,225; salt and pepper grinders for £2,618; a dizzying array of coffee machines and related coffee paraphernalia accounting for more than £10,000 of SNP members’ donations; a pencil sharpener, for heaven’s sake, costing £110.

A new £81,000 electric Jaguar appeared in the driveway – part funded by £57,500 of embezzled cash. There was a £2,500 jewellery box, a red tote bag costing almost £750 with which Ms Sturgeon was pictured cutting a dash, and two Dyson hairdryers – together worth more than £600 – purchased with stolen money by a man who is almost completely bald.

Once again, the former First Minister asks the public to believe she was oblivious to it all. She was as shocked and surprised as anyone to learn she shared a home with a common thief. She reminds us that she and Murrell both had high incomes and insists they had separate bank accounts.

Why would she jump to rash conclusions as her home steadily morphed into an Aladdin’s cave of ill-gotten, over-priced trinkets?

But her explanation raises many more questions than it answers. Such as this one. If we are to take Ms Sturgeon at her word, where does that leave the credibility of the predominant Scottish politician of the last decade?

Even among her admirers, it must paint her as naïve, unworldly and incurious in the extreme. It must mark her out as an appalling judge of character: this string of men she knew for decades but, it turns out, didn’t know at all.

One of them was her successor as First Minister, Humza Yousaf – the so-called ‘continuity candidate’ who had presided over failure and chaos in every government department he blundered into. Even party colleagues shuddered at his incompetence.

Yet Ms Sturgeon did not blanche until Mr Yousaf sacked the Scottish Greens from their power sharing agreement, torpedoed his premiership and plunged his party into crisis.

Now, in her eyes, he was guilty of a ‘catastrophic’ error of judgment. Many will wonder whether her own repeated failure to get the measure of those around her has proved equally catastrophic.

Ms Sturgeon, after all, was nothing if not the ‘details’ politician. She is asking people to believe she did not even question the details in her own home or in the character of the man she shared it with.

It gets worse than that. Those wedded to the notion of the former First Minister’s saintliness must now rake over the deeply troubling fall-out of the last few days.

It is reported Ms Sturgeon repeatedly replied ‘no comment’ during questioning by the police over the missing funds. 

This stonewalling, Scottish Conservative leader Russell Findlay reminds the Scottish parliament, is organised crime tactics.

If that was the reality, why did Miss Sturgeon say publicly before and after her arrest that she would co-operate fully with the police? And how does leaked video footage of a 2021 meeting of the SNP’s ruling NEC come across now that we know what was really going on?

In it a tetchy Ms Sturgeon attempts to shut down concerns about missing party funds, claiming – falsely – that they had never been in better shape. The clear message is ‘move on’. No more awkward questions please.

Ms Sturgeon’s airily dismissive attitude to those who questioned the wisdom of a party leader and a party chief executive living under the same roof also returns to sharp focus. 

It was Mr Salmond who strongly advised her to ask her husband to step down from the chief executive role when she took over as party leader and First Minister.

How prescient that counsel now seems. ‘I saw it differently,’ wrote Ms Sturgeon in her book.

‘By the time I became leader, Peter had been in post for many years. He was exceptionally good at the job. His role in turning the SNP into a modern, effective, election-winning machine cannot be overstated.

‘It seemed to me wrong that my election as leader should deprive him of a job he loved and the SNP of a highly successful chief executive?’ Wrong again. The decision to ignore critics of the cosy ‘cabal’ at the top of the party could scarcely have backfired more spectacularly.

There the First Minister lived under the same roof as the chief executive as their rooms groaned with the spoils of his looting sprees. 

She drank coffee made by machines paid for with money stolen from donations from the party faithful. 

The ridiculously expensive pen she used, the gold pendant she wore around her neck, the tote bag on her shoulder, the Scandi-noir DVD boxsets she loved to watch – all bought with plundered money.

Indeed, much as the brazen-ness of her estranged husband’s 12-years of thievery stretches the credulity of Ms Sturgeon’s position, if at all it is to be believed, it perhaps elicits a degree of sympathy too.

She was ‘oblivious’ to the facts behind the booty piling up under her nose in her own house, yet it is the absurd excess, the sheer frippery of the purchases which really twists the knife.

If, as she claims, she knew nothing of his criminal splurges, then the discovery of them has humiliated her more than any political opponent ever could. The man she married has made a complete fool of her, rendering a career camped out in the moral high ground a laughing stock.

But however much she knew, Scottish Labour deputy leader Jackie Baillie tells the Mail, she remains culpable. 

She says: ‘Throughout her tenure as the party’s leader, Nicola Sturgeon was renowned for her grasp of detail and her micromanagement of the party and the government. However, she expects us to now believe she simply didn’t know about the multiple scandals within the SNP over the years.

‘Either Sturgeon knew about the SNP’s rotten core and played a central role, with John Swinney, in covering up for the outrageous behaviour of now disgraced figures including her then husband Peter Murrell, or sex pests [such as] Derek Mackay – or she was so negligent that she allowed serious wrongdoing to occur on her watch, and even under her own roof.’

For her part – as one of the two longest serving MSPs – Dame Jackie stated this week it was ‘inconceivable’ Ms Sturgeon could have known nothing of the long-term fraud.

She adds: ‘During the Operation Branchform investigation, Nicola Sturgeon also maintained that she was co-operating fully with the police but it has now emerged that during a seven-hour interview all she said was “no comment”.

‘Nicola Sturgeon can attend as many book festivals as she likes, but she cannot hide from the fact that she has left behind a political legacy of failure, scandal, and cover-up, for which she should find the decency to apologise for.’

Questions over what Ms Sturgeon knew and at what point in the trajectory of this epic political scandal will doubtless dog her for the rest of her life. Did she lie to her party and the public? Is she, even now, lying to herself?

What is beyond question is her legacy – such as it was for the most divisive Scottish politician of modern times – is forever tainted. A postscript has been attached to her years as First Minister and it is so grievous that it rewrites the entire narrative.

She was a career politician, obsessed with the world of politics from her teens and standing for election to Westminster at just 21. For more than 30 years unshakeable conviction spilled out of her – often shrilly, always righteous in tone.

Even on the most sympathetic analysis, it seems there was much she did not know about the world, about people. Regrettable gaps, many would feel, in a politician’s qualifications for leading a nation.

It is too late. But maybe she is filling them now.