In the small hours of the morning, the phone rings beside Simon Hart’s bed. On the line is a drunk Tory MP, claiming to be stuck in a Bayswater brothel with a woman he thinks might be a KGB agent, who has just demanded £500 “and left me in a room with twelve naked women and CCTV”.

It sounds like something from The Thick of It, but for the chief whip to the last Conservative government, calls like this were all part of a day’s (or night’s) work.

“Amongst today’s HR joys,” he writes later “is the report from Emma [his special adviser] that a departmental spad went to an orgy over the weekend and ended up taking a crap on another person’s head. To make matters worse, in a separate incident a House employee went to a party dressed as Jimmy Savile and ended up having sex with a blow-up doll for which he has been subsequently dismissed.”

That this was light relief compared with some of what he dealt with underlines the diaries’ central message: that something has gone so wrong with the system by which people are selected, mentored and trained for parliament that running the country well has become almost impossible. Hart, who lost his seat in 2024, wants to show how “a relatively small cohort of people … knowingly made things so hard that what tiny chances we had of a fifth term were extinguished”. He does not, I suspect, mean the brothel-goers so much as the band of Brexiters, “oblivious to the numerical realities of what they were demanding” who – along with the former home secretary Suella Braverman – emerge particularly badly from this account. And if the wrong people make it into the Commons, wait till you see the pipeline to the Lords: Hart almost called his diaries “About My Knighthood”, given the amount of time absorbed by MPs trying to wangle honours for themselves.

This highly readable book is unusual in that, while its author served in cabinet for more than four years – as Welsh secretary under Boris Johnson and chief whip under Rishi Sunak – it is less an account of government than of what power did to the Conservative party, and thus to the rest of us. If you can’t quite place Hart, a One Nation-ish hunting and shooting type who used to run the Countryside Alliance, the portfolios he held were backroom ones taking him deep inside the plumbing and wiring of government. As Welsh secretary he was in on the big pandemic meetings, liaising with the devolved administration on lockdown rules. Later, as chief whip, he had a ringside seat on incessant plotting against various leaders, much of which sounds like something from a bygone age. (At one point during Johnson’s downfall, he writes of spiriting the chair of the 1922 Committee – keeper of the letters of no confidence from backbenchers which can trigger a leadership election – off shooting in Scotland “to keep [him] away from his inbox and buy some precious time”.)

Hart has a brilliant eye for moments of high farce: Jacob Rees-Mogg descending a zip wire in a tweed three-piece suit; Thérèse Coffey wanting to wheel-clamp people for Covid non-compliance; Kemi Badenoch existing in a “permanent state of outrage” that’s exhausting for everyone; Liz Truss’s spad explaining “the mayonnaise situation” (apparently she won’t eat anything containing mayonnaise, and will only drink Pret coffee). As for Lee Anderson, crowned deputy party chair only to defect to Reform, Hart writes: “I have tried to avoid the conclusion that he is a total knob but he has made it nearly impossible.”

Even allowing for the cabinet office’s red pen running through all ministerial memoirs, this one is remarkably discreet about both the substance and the deeper emotions of what actually happened inside government, skating strangely lightly over the surface of the pandemic in particular. Though Hart is plainly furious with Dominic Cummings over the latter’s not-quite-apology for his now infamous day trip to Barnard Castle, when the first stories start circulating about lockdown parties in Whitehall, he judges partygate “an odd story that I don’t think is resonating with the public”. Is having a beer with colleagues you’ve worked with all day really so bad, he wonders?

Instead, what begins as a diary intended as a lighthearted record for his children descends into something infinitely darker: a succession of entries about serious sex offences allegedly committed by MPs, and distressed victims seeking help that whips patently aren’t trained to give. The whips’ job, he writes, is less dark arts than field-hospital surgery, constantly patching up damaged people and sending them back to the front.

As an enforcer of discipline he seems empathetic, seeing most of the mess he has to sweep up as the consequence of “human frailties” and troubled people imploding under pressure. His is also one of the kinder portraits of working with Johnson I’ve read, presenting his downfall more as tragedy than scandal, though it still may not find favour in the former prime minister’s household. If you’ve ever wondered who started all those rumours about Carrie Johnson meddling, Lady Macbeth-like, in policy, it seems mostly to have been her husband, who in this account is forever moaning to colleagues behind her back. In one particularly wince-inducing vignette, Hart describes the PM chastising Scottish secretary Alister Jack for insisting that grouse shooting resume after lockdown because it’s led to wildlife-loving Carrie giving him grief: “to which AJ retorted ‘Well I’m sorry if you didn’t get your oats this weekend, PM, but this is the right decision.’”

But to its key question of why so many rogues end up in parliament, the book offers few explicit answers. This is somewhat puzzling given that Hart was responsible for party discipline and candidate vetting, and his own deputy Chris Pincher resigned over having drunkenly groped two men – a scandal that ultimately finished off the prime minister. (What did for Johnson was MPs’ fury that he’d given a man he’d once allegedly described as “Pincher by name, Pincher by nature” power over other MPs: Hart thinks it “implausible” Johnson hadn’t heard the rumours, but doesn’t elaborate on what he himself knew, or how the appointment was agreed.)

There’s a similarly awkward moment when his friend Neil Parish is caught watching porn on his phone in the Commons chamber, triggering a byelection. In the diary, Hart writes that of course “it was stupid and inappropriate, but I can’t help thinking if he was a factory worker he would get a written warning and sent on a course”. If an MP watching porn in sight of female colleagues, when he’s meant to be representing his constituents, is not seen as a deal-breaker by the chief whip, is he halfway to answering his own question about why the wrong people get on?

Though the diary entries are interspersed with short retrospective reflections, a perfect opportunity to suggest reforms, none are forthcoming. Ungovernable, or simply ungoverned?