Why would anyone want to be a politician? The pay isn’t great if you stay honest; the hours are long; the media attention you face can be brutal; your chances of getting anything done are slight unless you get to the very top. I should know. I was a politician in my native Canada for six years, and I have the scars to prove it. Although Americans think we are a kinder, gentler version of them, the fact is that our politics is just as nasty and partisan, and, after our Parliament Hill was occupied for three weeks by disgruntled truckers, sometimes just as wildly unpredictable. Social media has made it worse. When I used to meet constituents in the flesh, they were civil even if they weren’t ever going to vote for me, but digital disinhibition turns people into vipers. What some of my fellow citizens thought fit to say about me, and my opponents too, doesn’t bear repeating—and women have it much worse. Sigrid Kaag recently resigned as the leader of a Dutch liberal party, citing the “hate, intimidation and threats.”

So, truly, why does anyone bother?

A new memoir from Rory Stewart, How Not to Be a Politician, confirms why politics is a terrible way to live, but also why it continually lures ambitious people into the game. Stewart has written an unsparing and brilliant portrait of  his decade as a lawmaker, culminating in his failed bid to become prime minister. The lying, incompetence, and treachery he depicts are all so blatant that the book should be assigned to bright young things to rid them of any remaining illusions before they put their name on a ballot. But if Stewart has such a dim view of the whole enterprise, how can we understand why this gifted writer with a varied and unusual background, which includes being a Harvard professor and an administrator of an Iraqi province in the early 2000s, would choose to become a backbench member of Parliament for Penrith, a beautiful but remote constituency in the north of England?

In Stewart’s case, the usual mix of clichéd reasons apply—a desire to make a difference, do something that really matters, be part of history, serve the people, and, yes, get your name in lights. Fame certainly spurred him on, but for me, and for Stewart, I’m sure, something deeper than celebrity was at play: the belief that political success would give your life greater meaning and establish you, among those you respect, as a serious person. To all of this should be added the important fact that Stewart’s father was a courageous military officer, a distinguished member of the British secret service, and obviously an inspiration to his son.

You shouldn’t go into politics just to prove yourself—skydiving would be an easier path. One reason alone really justifies the effort, and all those slings and arrows: to get power and do something with it. Stewart did get power; he was a minister for the environment, international development, foreign affairs, and prisons in a ministerial career that lasted a scant five years. The portfolio range is staggering, and in each case he did his best to achieve something. But even when he was able to get his hands on the levers, it was often only to discover that getting things done is astonishingly difficult.

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Sometimes the obstacle was a fellow politician who would intrigue against him; sometimes it was a civil servant in his own department who would tell him, with a straight face, that what Stewart wanted to achieve was “above his pay grade”; sometimes it was, as when he was in charge of Britain’s international-aid program, uncovering that, with all kinds of good intentions, what aid programs from his country were doing was essentially shoveling money into bottomless pits all over the world. All of this led to the discouraging awareness, as he sat in splendid high-ceilinged offices created when Britain was a world power, that as a junior minister in a midsize post-imperial power that had just left the European Union, he could try to exercise his country’s influence globally, and nothing much would happen beyond a photo op.

Calling your memoir How Not to Be a Politician suggests that Stewart does not intend this to be an initiation narrative, in which our hero passes through painful stages, from innocence to experience. Rather, the book often reads like a discovery narrative, the hero’s dawning realization that the game was not worth the effort, that he has been duped by his own ambitions to play at something that wasn’t a match for his talents. Stewart had some difficulty hiding this epiphany from his colleagues, and that created a problem. Nothing is more fatal to a career in politics than leaving the impression that you think you are too good for it. The lifers, the men and women who live for the chance to run and run again for office, always resent people like Stewart, who have the strange idea that they are equipped for the job simply because they’ve succeeded in civilian life and think their amateurish earnestness entitles them to promotion.

Stewart was quick to pick up on this resentment, and he did what he could to earn his colleagues’ reluctant respect. He also realized that despite being an old Etonian and a graduate of Oxford’s Balliol College, and having had a stint of military service in an important regiment, he was an outsider to the party establishment. His years as a writer, during which he trekked across Afghanistan, set up a charity there, and established himself as a critic of international aid and development policy, marked him as “not one of us.” David Cameron, the super-posh prime minister when Stewart entered Parliament, ought to have seen his qualities and rewarded him with more responsibility. Instead, as Stewart describes it, one old Etonian froze the other one out.

All of this may seem of interest only to those who are fascinated by the archaic and arcane world of the British class system, but Stewart’s difficulties in elevating himself inside the Conservative Party illustrate the larger truth about politics everywhere: Tribalism abounds, along with customs only those lifers really understand. The three abiding rules are as follows: You must be loyal, you must wait your turn, and winning is everything. Stewart was too intelligent to be loyal, to shut up and bite his tongue. He was too impatient to respect the order of seniority that kept him off of key committee assignments in the House of Commons, though he did secure a place on the foreign-affairs committee, and his persistence eventually won him promotion to a cabinet post. And he obviously didn’t think winning was everything. Principle had to count for something. He developed a deep anger about the way the MPs in his party, who knew full well about Boris Johnson’s reputation for incompetence, still chose him as their candidate for prime minister in the 2019 elections; after all, Johnson was “a winner.” Stewart challenged Johnson for the leadership role, tried to unmask the false promises Johnson had made to his party and his country to get Brexit done, and was handily beaten.

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Stewart’s time in office is a cautionary tale about the price a politician can pay when he tries to tell the truth. Brexit, Britain’s referendum decision to exit the European Union in 2016, is turning out to be a multifaceted disaster, and Stewart, who campaigned to remain in the EU, was one of those who tried to get his party and his country to understand what a mistake they had made and then to figure out how, realistically, to make the best of a bad situation. He lost the race for leader, fundamentally, because he told his party what it did not want to hear. Once Johnson won the prime ministership, he threw Stewart and other like-minded MP’s out of the party and went on to win the next election decisively, with assurances that Stewart continued to insist were simply a pack of lies.

If living well is the best revenge, Stewart has had his revenge. Since exiting politics, he has run an international NGO that gives direct cash grants to empower poor communities in the developing world, and he hosts The Rest Is Politics, one of the most popular political podcasts in Britain. He’s said he won’t run in the next British election, due in 2024, but at 50, he has plenty of elections he could run in after that. The odd thing about Stewart’s story is that, having unmasked the reality of political life in the modern media age, he still appears fascinated rather than repelled by it. This revealing memoir goes to show that once you’ve been there, in the ring, in the middle of the fight, you never stop dreaming of climbing back in. Who knows? One day, he may.