Nicky Haslam has been writing his autobiography for as long as I’ve known him, which is nine years, but I never thought I’d live to see it finished. But lo! here it is, Redeeming Features by Nicky Haslam, not ghosted, 324 pages written by his own fair hand, and with a quote from AN Wilson on the cover proclaiming, “This Proustian evocation is indeed a masterpiece.” Fancy. According to Nicky, “It’s a memoir rather than an autobiography — there’s a huge difference.” The difference seems to be that he has felt free to leave stuff out: there’s a lot about his childhood and youth, but very little about the present day. He says he was afraid that if he wrote about the present it would “sound like name-dropping”, which is not a fear I ever knew he suffered from, but he swears he did. Did some of his friends ask him not to mention them?

“No! They love to be mentioned! People come and say to me, ‘Am I in it?’ And I say, ‘’Fraid not!’” Since his friends number in the thousands, there were bound to be some omissions. He regards himself as first and foremost an interior decorator — and certainly that is how he makes his living — but to the world at large he is better known as the man who knows “everyone”. Graydon Carter, the editor of Vanity Fair, calls him a “Zelig-like figure” who has been popping up at all the best parties for the past half century at least. He knew John F Kennedy and Andy Warhol and Cole Porter and the Windsors and Noël Coward; he is on chummy terms with most of the British aristocracy, including the royal family — he refers to the late Queen Mother by her insider nickname, “Cake”.

He was close to Princess Margaret, and even closer to her husband, Lord Snowdon (when he was still Tony Armstrong-Jones), with whom he claims to have had “a very brief romance”, and likewise her subsequent lover, Roddy Llewellyn. The Daily Mail went into a predictable frenzy at the thought of all this bisexual royal bed-hopping, and Snowdon issued a languid denial — “It’s not true as far as I’m concerned” — though Nicky claims that Snowdon was “amused” by the story and wished him well with the book. It is dedicated to Nicky’s seven godchildren, one of whom is Snowdon’s grandson. But since writing the book he has not heard from Llewellyn — now Sir Roderic and a happily married family man — and, perhaps for this reason, Nicky now insists he didn’t sleep with Llewellyn after all, although they lived together for a year. “I say we had a relationship. I’ve never once said we went to bed together. I never once imply it either.”

Oh, Nicky, you do! “No. I say I watched from my bed as Roddy got up in the morning — but my bed.”

But you say Lord Snowdon rang you up and said: “Get your boyfriend out of my wife’s bed.”

“You can call anyone a boyfriend, can’t you?”

Was Roddy upset?

“No — why should he be?”

Will some of his friends be annoyed by the book? “No, I don’t think so, because I haven’t written anything that would annoy anybody. I put something about Joan [Collins] “prowling between husbands” and she’s bound to hate the word prowling, but actually she was like a cat prowling, you know?”

The book is actually rather disappointingly discreet. Most of the shock-horror revelations are about people who are safely dead — he claims, for instance, that the Duke of Windsor and his brothers, Kent and Gloucester, were all bisexual because his old curtain-maker (now dead) remembered seeing them, in full slap, at a gay club, but this hardly seems conclusive. I was hoping for some account of why Nicky fell out with Cilla Black, who was his best best friend for a couple of years and then disappeared as if through a trap door, but she isn’t even mentioned. “Yes, isn’t it funny?” he agrees smoothly. “I don’t know why she’s not there.” This summer Nicky was staying with the Rothschilds on Corfu when Peter Mandelson was supposedly running the country from there and Colonel Gaddafi’s son was a fellow guest, but when I ask for some hints of their table talk, Nicky says maddeningly, “I know everything they talked about, everything, but no way will I reveal it” — and mimes zipping his lips.

But even with these omissions, his story is gripping, because he has led such an extraordinary life — a lonely childhood where he saw more of the servants than he did of his parents, undistinguished sojourns at prep school and Eton, then running around London with Bunny Roger, Cecil Beaton, Dickie Buckle, Stephen Tennant and all the higher pooferati, before teaming up with David Bailey and Jean Shrimpton to conquer New York. He worked at American Vogue under Diana Vreeland, and befriended Vogue’s young accessories illustrator, Andy Warhol (unfortunately destroying all his drawings as soon as he statted them), before going off with a rich boyfriend to live on a cowboy ranch in Arizona. Nicky as a cowboy is quite hard to imagine, but of course it gave him an excuse to wear chaps and spurs and stetsons and, as he admits in his book, “I think many episodes of my life have been predicated on wanting to look the part. Who hasn’t longed to be a cowboy?” He was blissfully happy and thought the Arizona idyll would last for ever, but the boyfriend fell for someone else and kicked him out. He arrived back in London, at 33, jobless and broke.

But Lord Hesketh, who had often been to stay at the ranch and admired its decor, asked Nicky to decorate his London flat, and other commissions followed. He was soon established as an interior designer and at just the right time, when his oldest, dearest friend, Min Hogg, was launching The World of Interiors magazine and interior design was all the rage.

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