The unseen Terry O'Neill: Unpublished portraits of the world's greatest stars

Terry O'Neill, sitting on a chair in a London gallery, leans forward on his haunches to peer at one of his own photographs, now four decades old, on a laptop computer. It's a picture of Mick Jagger in his prime, back when he still had flesh on those bones, as well as a preternatural pout he seems to have since handed on to Scarlett Johansson.

"Back in those days, we all used to hang out in the same clubs together," the 71-year-old says in his warming Ray Winstone-esque tones, a cloud of intensely strong aftershave surrounding his person like an invisible force field. "The Stones, the Beatles, all sorts of models and us photographers. You have to remember that, back then, photographers were often much more important than the pop groups they photographed. If I couldn't make it down to shoot Mick and the boys one week, then they would come to me. It was that sort of arrangement." He leans back, trailing his l'eau de Winstone scent, and nods his head in satisfied recollection. "I'll be honest with you: I don't think I could have come of age at a better time. I was 22 at the start of the Sixties. Best decade of my life."

The Chris Beetles Gallery in St James's, London, is about to host a retrospective of some of O'Neill's best work, much of it from the Sixties, including portraits of Audrey Hepburn, Lee Marvin and Chuck Berry, Marianne Faithfull, Peter Cook and Michael Caine. Most of it is previously unseen and only recently unearthed, this most celebrated of celebrity photographers having gone through his archives of late and come up with a batch of prints that he himself hasn't laid eyes on in almost a generation.

"I was lucky to find these," he says. "In the Sixties, most photographers never bothered to keep their negatives, so hundreds of my pictures, possibly thousands, are likely gone for ever. I certainly haven't got them. That's why it was such a pleasure, and a relief, to come across these."

The portraits have one common theme: intimacy – O'Neill having bagged the kind of candid shots that we tend not to see of our superstars any more. The whole thing reeks of sweet nostalgia for an era that the photographer himself still misses. "I used to be the Special Photographer on film sets," he says, "so nothing was closed to me. I'd spend weeks hanging around just waiting for the perfect picture. And I got them, simply because the stars were so relaxed around me. You don't get that nowadays, of course," he adds, laughing wryly, "because the PRs have stopped it. You're lucky if you get 15 minutes with one of the big actors today, but you can't really bond in that time, and so you can hardly be expected to take truly memorable shots. Instead, everything is posed, everything rushed. Nobody gets any really memorable pictures any more. Photographers these days? They have my sympathy."

Born in 1938 and raised in London, O'Neill grew up keen to become a jazz drummer. After a short stint in the army, he wanted to pursue his drumming in New York, and decided that the quickest – and cheapest – way to get there was to become an air steward for British Airways. He enrolled, but they promptly sent him to their photographic unit where he was dispatched to Heathrow to take pictures of travellers arriving, departing, saying hello and goodbye to loved ones. "There were lots of tears," he recalls.

He quickly struck lucky. One morning, he took a photograph of a man fast asleep on the floor of the terminal surrounded by some African chieftains. The sleeper turned out to be Rab Butler, then Britain's Foreign Minister. "The Daily Sketch loved it and published it," he recalls. "Next they wanted me to photograph this new band that was coming up ... the Beatles!"

When it was published, the newspaper sold out. The editor, realising that shots of celebrities shifted copies, wanted him to repeat the trick. Did he know of any other promising young bands? O'Neill recommended some friends of his, a blues group from Richmond called the Rolling Stones. This time the editor wasn't so impressed with the results. "He thought they were bloody ugly!" A week later, he photographed the more chiselled Dave Clark Five. The paper then ran pictures of both bands together under the headline "Beauty and the Beast" – O'Neill was relieved that Jagger saw the funny side to it. Once again, the newspapers flew off the stands, and the photographer's reputation was swiftly cemented. He was now, at the tender age of 21, one of Fleet Street's foremost celebrity snappers, leader of a new breed. His next commission was Laurence Olivier and John Mills in drag. His editor was overjoyed, and splashed the results over several pages.

"I was very lucky," he reflects. "Everything I touched turned to gold. But then that was the Sixties for you. It felt as if something brand new was happening every day. One day Mary Quant brings out something called the mini-skirt, the next day there's a new model on the block called Jean Shrimpton, and then Twiggy gets discovered."

And O'Neill was there to document it all.

"In many ways it was quite a revolutionary time," he says. "Before the Sixties, it was the toffs that ruled the arts, just as they did the country. But then the Sixties happened, and all of a sudden us poor people, your working classes, got a chance to show what we could do. It completely revitalised the arts scene, and it was bloody exciting."

By the late Seventies, O'Neill had settled temporarily in California, and was now photographing Hollywood's elite. It was there that he met, photographed and then married the actress Faye Dunaway (they divorced in 1986; O'Neill has since remarried), and went on to work for the likes of Vanity Fair, where he built up a formidable portfolio of, he says, "every actor you'd care to mention, the whole A-Z".

His photographs – of the great and the good, the debauched and, occasionally, the dying – have endured chiefly because they are so evocative of a time when a photographer was a friend and confidant to stars happy to be snapped without make-up or airbrushing, and without the interference of managers and PRs. "It was a golden age," he says. "And I'm glad I was around to capture it."

He still works sporadically these days, doing only what interests him, or else what pays the most. His next commission, he says, concerns royalty.

"I'm going off to photograph the Sultan of... um..."

Brunei?

"No, done him already. The other one. Abu Dhabi, the Sultan of Abu Dhabi." He smiles. "That's the fella!"

'Terry O'Neill: New & Unseen' is at Chris Beetles Gallery, London SW1, from 17 February. See chrisbeetles.com for details