The innocent reader might assume that writing a biography is an act of love. Writers know better. “The biographer at work, indeed, is like the professional burglar, breaking into a house, rifling through certain drawers that he has good reason to think contain the jewelry and money, and triumphantly bearing his loot away,” Janet Malcolm of The New Yorker wrote.

“Burglar” is a relatively flattering comparison. Tom Bower — the biographer of Tony Blair, Simon Cowell, the Sussexes and, in his latest book, the Beckhams — has been called the “Carlos the Jackal of contemporary biography” by the political journalist Michael White. Some writers choose subjects; Bower picks targets. “It is 339 pages of slaughter … every chapter, named, it feels like, after a Beckham fragrance — Revival, Dismay, Phony — portrays them as stupid, lying, grasping, mean,” Camilla Long writes in her review.

In this regard Bower is part of a grand tradition that goes back more than a century. Lytton Strachey’s Eminent Victorians, published in 1918, opened with a statement of intent about the biographer’s duties: “It is not his business to be complimentary; it is his business to lay bare the facts of the case as he understands them.” Strachey undersold himself. His brutal sketches demolished the entire mythology of the Victorian era as a time of high-minded public service as well as the reputations of his four subjects, including the nursing reformer Florence Nightingale.

Strachey described her as a woman who was demonically possessed: “Now demons, whatever else they may be, are full of interest. And so it happens that in the real Miss Nightingale there was more that was interesting than in the legendary one; there was also less that was agreeable.”

Tom Bower — the biographer of Tony Blair, Simon Cowell, the Sussexes and, in his latest book, the Beckhams — has been called the “Carlos the Jackal of contemporary biography.”

Nightingale is a byword for saintliness; other biographers have gone one better and ripped into actual saints. “Who would be so base as to pick on a wizened, shriveled old lady, well stricken in years, who has consecrated her entire life to the needy and the destitute?” asked Christopher Hitchens at the start of his exposé of Mother Teresa. The answer, of course, was that he would.

Mother Teresa in Hitchens’s version is no selfless servant of the poor. Instead she comes across as a self-promoting fraud, performing “modesty, humility and devotion” while acting as the head of what Hitchens called “a missionary multinational”. Taboo-savaging as it is, the book was merely a prelude to Hitchens’s later work assailing the whole concept of Christianity.

Hitchens also ripped into Bill Clinton as a “corrupt president” heading up a “corrupt and reactionary administration” in the book No One Left to Lie To. But Clinton’s reputation had already taken a kicking in the wake of the Lewinsky scandal. For a truly devastating shivving of a politician, look at John Charmley’s treatment of a British hero.

Churchill: The End of Glory, published in 1993, took a scalpel to a man still widely regarded as the UK’s greatest prime minister. But in Charmley’s account Churchill’s career is one of failure. He stood for the Empire and British independence and against socialism. The upshot of his leadership, Charmley claimed, was the collapse of empire, reliance on the US and a Labour government.

“Churchill’s leadership was inspiring, but at the end it was barren, it led nowhere and there were no heirs to his tradition,” Charmley declared. To compound the insult, the dust jacket of early editions featured a study for the portrait by Graham Sutherland that Churchill disliked so strongly his wife later ordered it destroyed.

Mother Teresa in Christopher Hitchens’s version is no selfless servant of the poor. Instead she comes across as a self-promoting fraud.

The primary victim of a biographical savaging is usually the subject, but sometimes it happens that a sympathetic portrayal of one individual creates collateral damage for another figure. That was the result of Anna Funder’s Wifedom: Mrs. Orwell’s Invisible Life, which came out last year. A revisionist life of George Orwell’s wife Eileen Blair, it (with the help of some heavily fictionalized passages) cast Orwell as a sadistic misogynist.

Luckily for Orwell, his supporters came out to defend his honor against Funder’s claims (some of which have been corrected for subsequent editions). Yet unpicking the damage of a vicious biography isn’t always so easy. Take the case of the comedian John Belushi, whose wife invited the journalist Bob Woodward (yes, the Watergate one) to write her husband’s story and came to regret it.

The resulting book, published in 1984, was called Wired: The Short Life and Fast Times of John Belushi and it unfairly cast its subject as a sloppy performer with a streak of cruelty, dominated by the addictions that ultimately killed him. Belushi’s friends and family disowned the work and Judith Belushi later recruited a second biographer in an attempt to overwrite the Woodward version.

Choosing a biographer is fraught with danger, but the unauthorized versions can be much worse, especially when a celebrity is protective of their image. America’s first family of reality TV was chronicled by Jerry Oppenheimer in the unauthorized blockbuster The Kardashians: An American Drama. Full of spicy allegations from anonymous sources, it scraped away at the glossy image of Kim and co, casting the matriarch Kris as a white trash social-climber “pimping” her “narcissistic, spoiled and glammed-up” daughters.

If biographers sometimes seem to hate their subjects with unusual passion, perhaps that’s because they have come to know them unusually well. Roger Lewis wrote a semi-deranged biography of Anthony Burgess (he was a “pretentious prick” and “a fake” as well as being superficial, crapulous and sanctimonious) that received a lot of flak. “[Reviewers] said, ‘Oh what we really want on Anthony Burgess is a proper literary biography,’” Lewis explained later. “That’s the last thing you want because Anthony Burgess was a great charlatan.”

And the animus can be even more intense when author and subject spend time together in person. Andrew O’Hagan was appointed as the ghostwriter for the biography of the WikiLeaks founder Julian Assange in 2011, but the relationship unraveled dramatically. The resulting book ended up being a sideshow; the main event was a 25,000-word essay by O’Hagan in the London Review of Books, describing their implosion.

After his last encounter with Assange, O’Hagan realized: “I was now making him into a figment of my imagination and that was perhaps all he could ever really be for me.” It sounds cruel, but as Janet Malcolm might have warned Assange: this is what happens when you invite the burglar in.

Sarah Ditum is a London-based journalist and the author of the book Toxic: Women, Fame, and the Tabloid 2000s