Nicky, darling: Deborah Ross pins down Nicky Haslam, Britain's busiest social butterfly

When I first call Nicky Haslam, the interior designer and fervent man-about-town, to arrange a meeting he says: "Shall we do dinner at The Wolseley?" "Yes, please," I say, "great." He then calls back and says: "I've booked, dinner at nine." "Great," I repeat, even though what I'm actually thinking is: nine? Nine? Heavens to Betsy, who on earth has dinner at nine? Seriously, this is my first thought. This is how old and boring and fusty and stay-at-home and washed-up I am. Heavens to Betsy, I even say "Heavens to Betsy" which no-one in their right mind says anymore. But nine? Who does go to dinner at nine? Only young people, I initially suppose, and Nicky Haslam, who is 70, but works so tirelessly at being young that it would be unspeakably cruel to exclude him.

So, to The Wolseley then, near Piccadilly, at nine – nine! – and you know what? It's packed. It's buzzing. It's happening. There's a whole world out there of people who don't do Masterchef and then go straight to bed. Everybody has dinner at nine! Why didn't anyone tell me? Why didn't anyone tell me again, once I refused to listen the first time? It's mad. I am early so wait in the bar while, yes, eagerly anticipating Nicky's arrival. I am keen to see what guise he'll turn up in tonight. Nicky once said it is everyone's "duty to look up-to-date" – not my duty, matey; I'm out way past my bedtime as it is, and that's all you're getting – and I'd read in some magazine or other that the Cossack look is in. I'm hoping he's adopted the Cossack look. Last time I met him – when I interviewed him in 2002 – he'd adopted the Liam Gallagher look: dyed black hair; torn jeans; leather jacket; that kind of thing. Ah, here is, and if I'm honest? I'm rather disappointed. His style is quite gamekeepery, wearing as he is a tweed cap teamed with a knitted tanktop ("from a thrift shop; I thought it rather pretty"), rust-coloured Topman trousers and Topman shoes "which are brand new but they make them look old. Isn't that funny?"

His hair is now its natural colour, a greyish white. I say I like it better than when it was dyed black. He says: "It's alright. I'd love it not to be this colour, but there comes a moment ... and it's sort of given it a new lease of life." I tell him I'm disappointed he's not wearing the Cossack look. He says: "I bought some girls' boots in Primark yesterday. Primark is quite good for shoes. They go up to here [he indicates knee-height] and there are tassels on the side and they look like part of a Ruritanian uniform. I was going to wear them but thought you might be shocked." How much? "Twenty-five quid." Leather? "Who cares!" He is surprisingly unsnobbish. We later laugh about "must-have" handbags. Or, as he puts it: "Pale-blue leather ones with huge studs on. Darling, you can't do worse, can you?" I said this in 2002 and will say it again now: Nicky Haslam could be a little ridiculous but isn't because he's just such fun, and always lifts your spirits somehow.

Anyway, we are directed to our table, although getting there is easier said than done. God, yes. Nicky knows everyone in the room. We pause, first, to say hello to the artist Lucien Freud. "Do you know Deborah Ross?" Nicky asks, rather as if Freud actually might, but as I didn't say in 2002 but will say now: the other thing about Nicky Haslam is that he treats absolutely everyone as if they are worth knowing, even when they are resolutely not. He is generous like that. We move on from Lucien, whom Nicky adores. "I've known him literally all my life. He's just a very sweet person. To other people he is difficult, but I find him so easy ... Rosita! ROSITA!" A woman – exceptionally well-groomed; meringue-type hair-do; Chanel fringed jacket or similar; looks as if she's spent all day choosing marble for her bathroom – is exiting but backtracks to give Nicky multiple air-kisses. "Do you know Deborah Ross?" he asks. She nods a "No, sorry" sort of nod, then departs. Who was that? I ask. "She's the Duchess of Marlborough," replies Nicky. "Well, one of the Duchesses of Marlborough. There is a new one now. She was the third. She's actually rather a good painter." I have since Wikipedia-ed her and can now tell you she was born Countess Dagmar Rosita Astrid Libertas Douglas-Stjernorp in Madrid, Spain, in 1943, the younger daughter of Count Carl Ludvig Douglas-Stjernorp (26 July 1908-21 January 1961), a Swedish nobleman and diplomat who was Royal Swedish Ambassador to Brazil, and his Prussian wife Ottora Maria Haas-Heye (13 February 1910-17 July 2001), maternal granddaughter of Philip, Prince of Eulenburg and Hertefeld. And she didn't know Deborah Ross? Heavens to Betsy, what kind of a world are we living in?

We settle at our table, finally. We order wine. I think we have quite a lot of wine. I have notes in my notebook that make no sense and seem to bear no relation to any conversation I can remember. Nicky's on a diet. He has just returned from ten days at the Mayo Clinic in Austria "where I lost a stone and half" which sounds a bit scary. He thinks he won't have a steak because, aside from the calories, "I find it very indigestible and will have to get the Tums out. I live on Tums. I love a Tum. Or Pepto-Bismol. I would eat Pepto-Bismol ice cream. I love it." He thinks he will have the cucumber salad and then the mussels. "Lucien always has the mussels," he says. "They are frightfully good."

He is a fabulous name-dropper; give him a name and he'll drop it. Don't give him a name, and he'll find one for himself, and drop it. There's a documentary about him due to go out shortly on BBC4, and, as he says: "If you watch it you'll see David Bailey saying that the Beatles were just a boring boy band and that 'It was Nicky, Jean [Shrimpton], Michael Caine and I who invented the Sixties'." Nicky has been promising to write his autobiography for years – has, in fact, been writing it for years – and now, amazingly, it is here. It's called Redeeming Features and is he proud of it? He is. "It's great that I really did do it myself," he says. "There is no ghosting at all. I feel it's a work. It feels like a proper part of my life." And what sort of feedback have you been getting? "Well, you mustn't quote me on this, as it's too awful, but Selina Hastings [the biographer] sent an email to Andrew Wilson [the writer], saying: 'I think you'll agree that darling Nicky's book is the most important social document of the 21st century.' Andrew wrote back to say: 'Yes, it's better than Proust.' I was so chuffed, but you can't put it in. You can't, you can't, you can't, you can't." Oh, dear. It looks like I just did. I do hope and pray he forgives me, but accept it's probably touch-and-go.

The book starts at the very beginning – his blissfully dysfunctional family; his polio as a child; his time at Eton – and then we are plunged into his totally compulsive networking. In London, it's Lady Diana Cooper, Cecil Beaton and Greta Garbo and then, in New York, it's Barbra Streisand, Marilyn Monroe, Andy Warhol, Mick Jagger and Diana Vreeland. Back to London and it's Wallis Simpson, the Queen Mother ... and so on. Nicky, is there anyone you've yet to meet but long to? "Obama," he says, "and Sandy Toksvig." Together? "Why not?" There is some lovely writing in the book – he describes one of his brothers as "poetically withdrawn", for example – plus there are some lovely details. I was particularly tickled by the notes Lady Diana Cooper would leave for traffic wardens when she parked illegally, as she always did. My favourite is: "Warden. So Sorry. Taking cross child to pictures. Please forgive." The juiciest gossip, though, has to be his claim that, in the 1950s, he had brief flings with both Tony Armstrong-Jones (before he married Princess Margaret and became Lord Snowdon) and Roddy Llewellyn (who became the Princess's lover). Snowdon has since denied it, and as for Llewellyn, Nicky now says nothing sexual ever went on. "I never used the word 'affair'," he says. "I only said I had a relationship with him." And that relationship was? "We shared a flat." I don't know, although suspect it's a case of poor Nicky, caught between the truth and friendship, which is never an easy place to be.

He was born at Great Hundbridge Manor, Buckinghamshire, to "Diamond" Louise Constance Ponsonby, one of Queen Victoria's god-daughters, although I'm not convinced she was a favourite god-daughter. When the Queen died she left Diamond a purple pin-cushion, which doesn't seem a lot, considering she was the Queen and everything. Where is that pin cushion now, anyhow? "Gone," he says despairingly. Where? "No idea." He then adds: "There was a Lowry for sale at Christies, quite a boring one, a view of the Thames, which sold for £600,000. It was my father's and we sold it for nothing when he died. Makes you sick, doesn't it? It really makes one furious. I sold my Andy Warhol thinking: it will never get more valuable than this. Oh, the stupid things one does."

His father, William, came from a background of rich Yorkshire trade based on the cotton mills. (The Haslams, as it happens, invented Aertex, so if you've ever shivered in the stuff as an outside fielder at rounders at school, you now know who to blame.) His parents courtship was curious. Initially, William rejected Diamond who, in response, fled to New York, married someone else and had a child, at which point William decided he had to have her, arrived in New York, and seduced her away. I say "curious" because from reading the book, I don't feel there was actually much love between Diamond and William. Was there? "I think she loved him," replies Nicky. "She left a very glamorous life. England in the Thirties was very parochial compared to New York. Did he love my mother? I'm not sure." Did you feel loved by your parents? "Not unloved," he says, "but in those days people didn't express love that much. It would have been considered common." Do you think your father could love? "I'm tempted to say 'No'..." he pauses, and goes quiet. I think there might be a tear in his eye. He then continues with: "He was very ... inner. He used to write the names in the visitor's book at Hundbridge himself." What do you mean? "If HG Wells came to stay, my father would write 'HG Wells' in the visitor's book. He'd never have asked HG Wells himself to sign it." Are you saying that actual people weren't important to him? "Yes. He cared much more about historical veracity." So the fact that the signature wasn't in Wells' hand wouldn't have mattered? What mattered was only that the visit was recorded? "That's what he was like. He was very introverted."

What do you imagine he thought of you? "He thought I was a feckless, hopeless, lazy ..." When his father died in 1988, Nicky discovered he'd been cut out of his will. Wow, I say, that must have hurt. He says: "I was more surprised than hurt. I didn't quite see why he'd done it. He probably had a good reason. My mother was rather astonished by it." Was there much to leave, by that point? "Well, he left quite a nice lump to my two brothers. I'm not talking multi-millions, but enough to make it worthwhile having."

I wonder if, denied paternal love and approval, Nicky has since been seeking both elsewhere. Is this what all the networking and party-going is actually all about? Goddamn it, my father didn't rate me, but everyone else will. Do you still, Nicky, go to 79 parties a night? "If they sound good and interesting, yes," he says. He then recognises a passing couple and exclaims: "Mrs Bass! Mr Bass ... Sid! Do you know Deborah Ross?" I later look up Mr Bass. He is Sid Richardson Bass (born 1942), an American investor and billionaire, listed as the 287th richest person in the world in Forbes with a net worth of US$3 billion. And he doesn't know Deborah Ross? I despair.

We eat our late dinner, and talk about his work. You may not particularly like his decorating style – I'd call it 18th-century rich dowager – but it is a serious business, and he currently has 14 projects on the go. Nicky, needless to say, works at the upper end of the market. Bryan Ferry, Charles Saatchi and the Prince of Wales have all been clients, as have umpteen Euro-princelings and, latterly, all the newly minted Russians. How would you describe your style, Nicky? "I'm not one of those decorators who puts four white trunks in a pile and a melon on top. That's a stylist. I'm an actual decorator. I will make rooms look perfect by adding the things it needs and taking away the things that ruin it." He lives in a basement flat in west London, opposite the Natural History Museum, which is where I interviewed him in 2002 and which, if I recall rightly, was very dark and plum. He also rents a Hampshire hunting lodge from the National Trust, which is where he mostly goes at weekends. "You must come, darling, it is heavenly." Do you, I ask, have a boyfriend at the minute? "Sort of, very gently," he says. "He's a handsome young film-maker." He has had three long-term relationships over the years and has never been promiscuous. I don't even think he's that sexual. He says in the book that he's always had "withdrawn feelings about physical sex" so I'm guessing he's more the romantic sort. He confirms he is. "Certainly, I didn't feel part of the new generation ... whenever they go out, they want to pick up somebody, take them home, and screw them all night. I like writing notes." Have you ever fretted about being gay? "Never," he says.

Anyway, it's getting very late now, a lot of wine has been drunk, Kate Ford – "wife of Henry, the motorcar man" – doesn't know me, and now it's time to go. Nicky kindly walks me to Green Park tube, where we part affectionately. One thing, though, before I sign off and you all write in: although a lot of names were dropped during the putting-together of this article, none were harmed. End of.

'Redeeming Features' is published by Jonathan Cape, £25. The BBC4 documentary will be shown on 16 November.