John Swannell: 40 years of portraits from a modern master

John Swannell keeps a diary, with pictures and words. It's pretty flash. In fact it's a bit like flipping through Tatler. Tara P-T today. Darcey Bussell here, Tony and Cherie there ("Cherie has great skin – like marble"). And there's Lady Bamford, millionaire and organic jam-maker, who recently commissioned him to take her passport photo. Following in the time-honoured tradition of Donatella Versace, whose passport picture is by Steven Meisel, Lady Bamford logically concluded that if it has to last 10 years, it might as well be good. A chauffeur brought her round to the studio. "Life," Swannell smiles through his round Hockney glasses, "is a lot of fun."

The well-beloved celebrity portraitist is sitting at home in Hampstead, which he shares with his second wife, Marianne, and their two children, as well as his favourite Pre-Raphaelite paintings (only Pre-Raphaelite lite, as Andrew Lloyd Webber has snapped up all the good ones, damn him!). Romance has always been his thing. Ten or so years younger than Bailey and his gang (Terry O'Neill, Terence Donovan), Swannell lacks their acerbic eye. His is a gentler, more old-fashioned philosophy: "I think women should look beautiful, and men should look interesting. And everyone looks better with a little retouching." You can see why he's so successful.

But Swannell is also highly rated by the cognoscenti. The National Portrait Gallery owns 76 of his works."He's extraordinarily good at formal portraits," says its director Sandy Nairne, "and equally good at the more off-guard ones where he catches someone at a telling angle. He's a bit of a master, really."

Sitters are also admiring. "I'm very fond of him," says Marie Helvin. "In his viewfinder, all women become swans." Michael Palin adds: "He's disarming... there is no sense of an ego at work here." What's his secret? "I'm very quick," he says. "With people that are talented and famous, time is of the essence so I tell them, 'It'll be over before you know it', and that cheers them up." He makes it sound like dentistry – now that's unpretentious.

He doesn't need to be that way. He has a lifetime of good credentials to flaunt. The walls of his corridors are covered with a valuable collection of prints he's amassed over the years: Bailey, Lartigue, Sarah Moon, Richard Avedon, Bill Brandt... However, he has recently sold his Helmut Newton print. "Helmut took a liking to my battered old camera bag. He was always on about how much he wanted it. In the end I gave it to him in return for the print of the cover of his latest book, White Women. I went off the subject-matter a bit, so I recently sold it at Christie's New York for $23,000." Which is something of a good deal, considering the camera bag came from Oxfam.

In the loo, there's a cute contact sheet of him and Bailey in the late Sixties, leaning on one another, pulling poses in their flares and Donovan caps. Bailey looks lordly, Swannell terrified. He had just been appointed assistant to Bailey: his childhood dream come true. Born in 1946, Swannell grew up "just down the hill" in Finsbury Park, not academic (he's dyslexic) but photo-mad from the get-go. "I was always converting our bathroom into a darkroom..." His mother must have been pleased when he found another photo lab on Fleet Street, where he worked on a newspaper for a few years.

Next stop was the hallowed Vogue Studios, where he watched and learnt from Richard Avedon (his all-time favourite photographer) – and was recruited by Bailey. "He had this incredible tenacious determination," remembers Bailey. "And was always an incurable romantic...". Swannell found himself being chauffeur-driven to Stonehenge to shoot the Rolling Stones album cover, and sharing a joint with John Lennon. As his own career blossomed, the fun continued.

One of his first solo assignments was to photograph John Hurt, who had just made The Naked Civil Servant. "I was so nervous I did all the research I could. I phoned round and found someone who vaguely knew him, who told me that Hurt liked a drink. So I got a few bottles of champagne in. We ended up drinking all day, from 10.30 in the morning to 1.30am." But were the photos in focus? "I could hold my drink well then – I was only 25. At the end of the shoot we were staggering up the road, arm in arm like a couple of gays."

Swannell says that, most of the time, he works by instinct: "Planning is impossible. Usually it's a wing and a prayer." He enjoys accidental felicities. He was photographing Robert Mapplethorpe informally in 1980 (it was one of those indulgent "Can I photograph you? And can I photograph you back?" trade-offs that photographers like to do, he says) when the studio backdrop fell down. "My assistant ran to put it back, but I stopped him as I really liked it half-collapsed."

At other times, preparation is key. In 1994, Anne Harvey, assistant editor at Vogue magazine, rang to book him for a session, only she couldn't tell him who it was going to be with. "Finally she told me it was Princess Diana and her boys, who were about 10 and 12 at the time. So I had a table tennis table set up in my studio, to stop them getting bored." While Princess Diana was having her make-up done, Swannell beat the heir to the throne at ping-pong. Harry, however, thrashed him. The resulting pictures were very relaxed and happy, and Diana used one as her Christmas card. "I think it was the independent, 'up' picture of her with her children that she wanted," Swannell says.

Since then he has shot almost all the other members of the royal family (some less successfully than others – the Daily Record called his postal-stamp shots of Prince Edward and Sophie Wessex "nauseating") including several sessions with the Queen. She even let him tempt her on to the Windsor Castle battlements in her full regalia, though the pictures have never yet been seen.

Looking back over his career, Swannell can't believe how many hours he spent closeted away in his dark room. The digital revolution has been "fantastic". Across his oeuvre he rejects the more experimental work. A Duran Duran album cover shot in infra-red "looks dated now", he thinks. "The tricksy stuff won't last," he concludes. "Only the classics."

An exhibition of his portraits is at the Chris Beetles Gallery, London SW1 (020-7839 7551), Wednesday to 5 April, and Swannell is speaking at the Royal Geographical Society, London SW7 (020-7033 3878) on 8 April at 7pm, in aid of Photo Voice