Never-ending stories: Is there anything left for biographers to reveal?

A hot news item from the 1940s was announced this week. On the Gawker website, in The Washington Post, in Agence France-Presse, the big revelation was splashed for all to see: Coco Chanel, the great fashion designer, clothes horse and begetter of the world's most famous perfume, spied for the Nazis during the Second World War.

Seventy years after the events, the news caused a stir. "Coco Chanel spent WWII collaborating with the Nazis, says a new book that outlines her life," reported the Daily Mail, going on to quote from the book Sleeping with the Enemy: Coco Chanel, Nazi Agent by Hal Vaughan, who claims that the grande dame of the little black dress was practically a Nazi herself: "Fiercely anti-Semitic long before it became a question of pleasing the Germans, she became rich by catering to the very rich and shared their dislike of Jews, trade unions, socialism, Freemasons and Communism."

The book also claims that "in 1940 Coco was recruited into the Abwehr and had a lover, Baron Hans Günther von Dincklage, who was honoured by Hitler and Goebbels in the war".

One's first response is to wonder whether Ms Chanel ever linked up with Hugo Boss, who designed the Nazi uniform and whose career blithely survived the war despite the taint of fascism. One's second response is to say: I thought we knew this stuff about the Nazi lover already. And a third is to wonder: how much more information about Coco bloody Chanel do I need in my life?

It seems only yesterday that Justine Picardie's Coco Chanel: The Legend and the Life was garnering enthusiastic reviews for cutting through "the accretions of lies and romance" that surround Chanel's reputation. It came out in 2009, the same year as The Gospel According to Coco Chanel: Life Lessons from the World's Most Elegant Woman by Karen Karbo and Chesley McLaren, one of a number of self-help and picture-heavy tomes that accompanied the release of Anne Fontaine's movie Coco before Chanel starring the lovely Audrey Tautou (who, of course, also starred in the last big Chanel perfume television commercial) and, coincidentally, Jan Kounen's film Coco Chanel & Igor Stravinsky, which opened a few months later, starring Anna Mouglalis as the scissor-wielding horizontale.

Die-hard fans might already have been familiar with Chanel and Her World: Friends, Fashion and Fame by Edmonde Charles-Roux, published four years earlier, or indeed a full biography entitled Coco Chanel by Henry Gidel published in 2000 – or indeed they could have checked out a book called Chanel: A Woman of Her Own by Axel Madsen published by Bloomsbury as far back as 1991. It deals with her famous lovers (Cocteau, Stravinsky, Dali, the Duke of Westminster) and tells all about her German boyfriend, and her crackpot attempts to convey German peace proposals to Winston Churchill, whom she had met earlier through the Duke.

In other words, we knew most of the Nazi stuff 20 years ago. If we'd forgotten, the publication of the French historian Patrick Buisson's Erotic Years 1940-1945 in 2008 would have reminded us that Chanel spent most of the war in the Paris Ritz Hotel, that her boyfriend was the amusingly named Baron Hans Günther von Dincklage, and that he was a military attaché with the German embassy and a famous spy. Half of Paris knew about her liaison at the time, and condemned her for it. She herself claimed she'd used her affair with Baron Von Dincklage in order to meet a high-up general, in order to broker a peace deal with the Allies.

Perhaps this is what Hal Vaughan, the author of the new biography, means when he accuses her of "dabbling in Nazi foreign policy". He also accuses her of being "fiercely anti-Semitic", in using anti-Jew laws to close down a company to which she'd sold perfume-making rights to Chanel No 5. But as Justine Picardie argued in her biography, this unpleasant episode reeks more of commercial ruthlessness than of race hatred. Coco was, from first to last, a hard-faced, hard-nosed businesswoman with a flair for self-promotion and self-preservation. She slept with people she fancied, whether they were Nazi spies or English aristocrats. She did whatever it took to survive. And she lied and lied about her life, from the date of her birth to her upbringing in an orphanage, to her years as a demi-mondaine, one rung up from a prostitute.

So now, we have Hal Vaughan's slightly vieux-chapeau revelations about wartime espionage (the only intriguing detail in his account is that Chanel was allegedly recruited to the Abwehr military intelligence organisation under the code name of Agent F-7124 – though she was later accused by the Nazis of being a British spy), and that will do for the moment, won't it?

Well, no, actually – amazingly, there's another work in the pipeline, Chanel: an Intimate Life by Lisa Chaney, to be published in November this year. Mercifully, it starts in 1945, when her wartime shenanigans were over, but it shockingly reveals that, at some point after the war, the designer had sex with a woman, and occasionally indulged in "opiates", as the blurb quaintly calls them. As revelations go, these inhabit the same space as the information that ursine quadrupeds relieve themselves in leafy environs. Whoever thought it was worth commissioning another Coco book on the strength of some teeny details of sex and drugs?

Which raises the crucial question: what does it take to justify a biography today? What makes a publisher think that a dead person's life is worth the general reader's attention again? What makes it worth joining a herd of other authors writing about the same life?

The unofficial rules of "life-writing" used to hold that to publish a biography of a canonical figure (ie, one safely dead and consigned to a generally agreed "place" in history) less than 30 years after the last attempt, is a waste of both time and academic energy. Once Boswell had "done" Johnson, it was tacitly agreed, there was no need of another "life of" for a generation or two. The latter half of the 20th century, however, rewrote the rules. A new frankness in discussing sexual matters, a fascination with the minutiae of famous lives. A prurient interest in what was once deemed shocking behaviour, a wholesale lack of interest in Victorian-style hagiography – these all changed the face of biography in the late 1970s and 1980s.

Suddenly, you didn't have to wait 20 or 30 years if you had some juicy new information or some shocking new theory about the lives of the famous. Five years would do – or less. Victoria Glendinning recalled how amazed she was, when embarking on a new life of Anthony Trollope, to discover that three other Trollope biographers were already hard at work. The life-writing genre was suddenly deafened by the noise of tightly shut closets being flung open. New caches of letters, diaries and previously unseen material easily justified new lives of Victorian authors, politicians and adventurers, of Edwardian suffragettes, Bloomsbury intellectuals, pre-war sportsmen, post-war entertainers.

Shocking material, hitherto unpublishable, was suddenly available to all. John Lahr's sprightly life of the Sixties playwright Joe Orton, Prick Up Your Ears, with its frank account of gay high-jinks in public lavatories, could never have seen the light of publication before 1987. When Fiona MacCarthy brought out her life of Eric Gill, the sculptor and typographer, in 1989, she revealed to the world that he'd slept with every woman in his saintly Catholic commune in Wales, including maidservants, the wives of friends, his sisters, his two daughters – even the family dog. The facts had been available for years, explicitly laid out in Gill's self-accusing journals, but earlier biographers had been too cautious (or their publishers too shocked) to use it.

Some readers objected about what they regarded as a retrospective invasion of a subject's privacy, but their objections were brushed aside. "When you get the truth told without censure, then you realise how very various human nature is," Michael Holroyd, the doyen of biographers, told The Times. "The biographer's loyalty has to be the subject, and not what peripheral people are going to think about it."

Historical or literary figures about whose lives we'd speculated became fair game for several investigations. Hints of paedophilia or repressed sexuality became a focus of new biographies. Lewis Carroll's interest in, and photographs of, half-dressed little girls (and his artless letters to their parents) prompted a small industry of books. The lives of heroic figures with inscrutable emotional lives – Sir Robert Baden-Powell, founder of the Boy Scouts, Sir Richard Burton, explorer and translator of the Kama Sutra – were inspected for signs of perversity. It was fantastic. Furtive sensation-seekers, too wary to look for sexually explicit material on bookshop shelves, could get their kicks in biographies – if they didn't mind ploughing their way through 500 pages of extraneous material.

Today, prurient browsers with a fascination for reading about physical or sexual abuse can easily find them in the pages of the popular "misery memoir". The biographies in the modern best-seller lists are mostly lives of living celebrities and entertainers, with their own protocols of revelation, modesty and nuance. For an author to justify writing the life of a canonical figure, however, the rules are different. The biography doesn't have to be about sexual revelation any more. It's more likely to be about truth and identity. "A good biography," says DJ Taylor, author of lives of Thackeray and George Orwell, "should be about what Anthony Powell calls 'the personal myth' – not about what the subject did, but about the image of themselves that they projected to the world. Who they thought they were, what they think happened to them – and what the truth actually was."

That's precisely the double-perspective that has informed several recent literary biographies: John Carey's life of William Golding, which incorporates a huge, self-flagellating, million-word diary kept by the author of Lord of the Flies; Gordon Bowker's life of James Joyce, which constantly asks the question of exactly how "Irish" the author of Ulysses was, and thought himself to be. And it can be applied in spades to Coco Chanel, a woman who was forever at pains to project an image of fairy-tale sophistication.

She faked so much of her long and phenomenally successful life, it's hardly surprising biographers have queued up to try their luck at disinterring the truth – and are still doing so. In penury and plenty, in peace and war, in bedroom and showroom, there's plenty of Chanel's life to go round for the truffle-hunting truth-hound. And she knew very well what she was doing. "Reality is sad," she once said when living in Switzerland after the war, "and that handsome parasite that is the imagination will always be preferred to it. May my legend gain ground; I wish it a long and happy life."