The history of Malcolm Turnbull’s prime ministership might have been very different were it not for an extraordinary blind spot that he claims prevented him from seeing the threat of Peter Dutton.

Turnbull is, famously, a man of remarkable intelligence. In his autobiography A Bigger Picture, which includes his account of his time, and eventual downfall, as prime minister, he acknowledges an extraordinary failure of judgement around Dutton.

Dutton was the cloddish Queenslander who, during the Coalition’s time in government, blundered through the health portfolio and then repeated the underperformance in Immigration/Home Affairs — the portfolio that has emerged as by far the most incompetent and scandal-prone department in the Commonwealth.

Turnbull writes:

I’ve always assumed people have a reasonable amount of self- awareness and Dutton had never struck me as being so self-delusional and narcissistic as to imagine that he could successfully lead the Liberal Party. More relevantly, it had never occurred to me that others would think he could either.

Turnbull, it seems, can’t quite believe everyone else doesn’t understand how disastrous Dutton would be as leader — a view Turnbull says Kerry Stokes shared when they discussed the News Corp campaign undermining his leadership.

But others don’t share his view. Christopher Pyne and Julie Bishop warn Turnbull that Dutton is stalking him. So too does George Brandis, who after Turnbull’s ouster writes to him:

Your fatal mistake was, of course, to trust Dutton. If I may say so, I, and others, warned you many times that he was stalking you, and that his ‘support’ for you would be rescinded the moment he saw the opportunity to seize the leadership … Malcolm, you trusted the wrong people.

There are multiple ironies in Brandis’ observations (and Turnbull says he can’t recall Brandis warning him about Dutton).

Brandis as attorney-general was almost as much of a dud as Dutton, although it is to his credit that, unlike his wretched successor Christian Porter, he resisted the vexatious prosecutions of Witness K and Bernard Collaery.

But most of all, Brandis was the chief victim of Turnbull’s promotion of Dutton. It was Brandis who lost key parts of his portfolio, including ASIO and the AFP, to the creation of the Home Affairs “super portfolio” for Dutton, an act that merely gave Dutton and his functionaries a bigger stage on which to stumble and blunder.

What’s all the more remarkable about Turnbull’s blind spot about Dutton is that it was hardly for want of public commentary about the ambitions of the Queenslander. That Dutton was interested in the leadership was a staple of political commentary in the Turnbull years, whether at Fairfax, News Corp, the ABC, or doyenne.

Many even interpreted Turnbull’s promotion of Dutton to Home Affairs minister — at the expense of humiliating a fellow moderate in Brandis — as an effort to keep Dutton on side and in check.

It’s thus more than a little implausible for Turnbull to claim the idea that Dutton really did fancy himself as PM material hadn’t occurred to him, though his judgement that his party colleagues — men and women paid to live and breathe politics and stay in touch with their constituents — were smart enough to realise he wasn’t does ring a little truer.

Some of the funnier moments in the book involve the efforts of Kevin Rudd to get Turnbull’s endorsement for his run as UN Secretary-General. Julie Bishop thinks the government should be bipartisan and back Rudd, but Turnbull and half his cabinet think the former PM is wildly unsuited to such a job given his temperament.

When Turnbull informs him of his definitive no, Rudd — as has already been reported and confirmed by the man himself — erupts into a stream of obscenity-laden invective.

“Don’t you see this is just confirming what I’ve said to you,” Turnbull replies. “You don’t get what you want and immediately you are screaming at me, swearing at me, threatening me. Don’t you think this is a bit unedifying you doing this, an ex-PM to the current PM?”

Particularly funny is that Turnbull is — correctly — accusing Rudd of a character flaw that he himself long possessed in spades.

Rudd and Turnbull are remarkably similar: brilliant minds, unbounded ambition and a raging fury for those who disagreed with them.

Except, within Turnbull you always sensed there was an actual human being, however flawed and prone to misjudgment.