From Audrey Hepburn to the Beatles, Frank Sinatra and Elton John, there aren’t many pop cultural icons Terry O’Neill hasn’t photographed. One of his subjects, Hollywood actress Faye Dunaway – who he famously captured hungover, surrounded by newspapers the morning after winning an Oscar in 1977 – became his wife, even if the memory now frustrates him. He agrees that a photographer falling in love with one of their subjects is rarely a good idea: “That was a waste of 12 years of my life!”

Yet the legendary photographer insists none of these stars compared to David Bowie. “He was my creative muse,” O’Neill tells me authoritatively over the phone. “He was so charming and warm, and one of the few people [other than Faye] I really felt friendly towards.”

The flash startled the dog … a session for the Diamond Dogs album. Photograph: Terry O’Neill/Iconic Images

Currently suffering from prostate cancer, O’Neill is confined to bed and admits that he’s severely lacking in energy. But the mention of Bowie will occasionally cause the 81-year-old’s hoarse cockney drawl to soften and lighten up with enthusiasm.

“I treated David like a Shakespearean actor as you never knew who was going to show up,” he says affectionately. “He could look alien-like or female-like; it was always so exciting as everything he did was so unpredictable.”

Over a 20-year period, O’Neill captured Bowie’s shapeshifting artistry better than just about anybody else, standing behind the camera as the Space Oddity singer transformed into theatrical glam avatar Ziggy Stardust, then morphed into the coke-addled Thin White Duke, who in 1976 notoriously told Rolling Stone’s Cameron Crowe: “I think I might have been a bloody good Hitler. I’d be an excellent dictator.” Although, O’Neill claims: “I don’t actually remember him saying that stuff.”

His last magazine shoot with Bowie in 1992 was shot like a sentimental happy ending, with O’Neill’s warm closeups giving off the impression he was delighted the star had managed to make it out of the 1970s alive. “It felt like we had come full circle,” he agrees.

O’Neill’s photographs have left such a lasting impression because he was able to demystify some of the 20th century’s biggest icons and cut to the core of their personalities. His photographs of Audrey Hepburn, for example, went beyond the clichés of her delicate beauty and prioritised her goofy side, as she pulled silly faces while relaxing by the pool.

The imperious strength of Winston Churchill, meanwhile, is something O’Neill ripped into pieces. Instead, we saw a frail old man who was admirably trying to keep up the illusion of the cigar-munching British Bulldog despite the fact he had become so weak he had to be carried around in a chair by minders. “It was 1962 and I was going home from the office and saw this crowd forming,” he recalls. “I burst my way through it to take a photograph and it was Churchill leaving the hospital. I didn’t really know his whole story so I just shot what was in front of me. The fact I didn’t have any emotional baggage maybe helped.”

Farewell Ziggy … Stardust’s final outing, for an NBC late-night show in London, 1973. Photograph: Terry O’Neill/Iconic Images

Three years earlier, O’Neill had started working at the Daily Sketch, becoming one of the youngest photographers on Fleet Street. “I wanted to be just like W Eugene Smith, who was such a great photojournalist. His images were full of truth.” One of the first important gigs he can remember taking on was photographing Laurence Olivier dressed as a woman for a performance at the London variety show The Night of a Hundred Stars; perfect training for the gender fluidity of Bowie that would await him later on. “There was a 12-year-age gap between me and the next youngest photographer,” he recalls.

According to O’Neill, nobody in Fleet Street wanted to interact with the youth scene and its emerging bands, such as the Beatles and the Rolling Stones. This left him with an opportunity to capture the swinging 60s with real freedom. “I remember I was asked by an editor to go photograph this ‘little band’ called the Beatles at Abbey Road Studios, then that led to me working with the Stones,” says O’Neill. “All the old timers didn’t want to take these photographs on and almost looked down on them. It meant us youngsters could jump in and take up the opportunity. I could go out and create my own world. There was no other time like it; it was just so much fun!”

By the time O’Neill started shooting Bowie during his Ziggy Stardust tour in 1973, he was much more of a respected name in the photography world. But while he had taken important concert photographs before, O’Neill was able to enjoy these ones a lot more. “You couldn’t bloody hear the Beatles,” he explains, “but Bowie’s show actually entertained you and had a story to it. I could hear every word and he really gave you a proper show.”

Scantily clad in fishnets and monster claws over his chest, rocking a garishly orange mullet, Bowie’s on-stage “bravery” during this era impressed O’Neill, especially the way he wasn’t afraid to look effeminate at a time where this could get you beaten up. Most of all, he liked the fact that Bowie took charge of his own image during their sessions, particularly for their Diamond Dogs shoot, where the singer had a specific, animalistic, bare-chested pose in mind. He also brought a dog on to the set, which jumped up in shock at the flash of the strobe lighting, perfectly capturing the kind of avant garde chaos Bowie had intended for his dystopian album, influenced by George Orwell’s 1984.

A contact sheet from the Diamond Dogs shoot. Photograph: Terry O’Neill/Iconic Images

“I loved that he had all these characters and took charge of our sessions and told me exactly what he wanted,” says O’Neill. “It meant that our pictures had a purpose. I guess with most of the other pop stars I shot, it was sometimes very aimless. With David, you never had to coax things out, they just came naturally.”

Yet just a year later, during a shoot for the Los Angeles Magazine, O’Neill could almost be photographing a different person – Bowie appears gaunt and looks like he hasn’t been sleeping. “There was a lot of cocaine all of a sudden,” admits O’Neill. “He was really big on drugs. I never felt I was in a position to have a word with him about it as don’t forget: we were all around the same age!”

One of O’Neill’s most famous Bowie shots co-stars a fellow countercultural hero. “One day he told me, ‘Come to my office tomorrow, I’m bringing someone special.’ I got there and it was William Burroughs, and I was completely staggered. They were both dressed in fedora hats like father and son,” he giggles. Was that the Naked Lunch author’s idea? “No, David decided on that.”

‘I’m bringing someone special’ … with William Burroughs for Rolling Stone in February, 1974. Photograph: Terry O’Neill/Terry O'Neill

Around this period, O’Neill heard that Elizabeth Taylor was hoping to cast Bowie in her new movie Blue Bird, so engineered a shoot between the pair. But Bowie, who was by this stage doing lines of coke for breakfast, showed up four hours late. “It was only because of Liz’s professionalism that the shoot even happened,” he reflects. “David showed up stoned out of his head.” In these photographs, Taylor looks bemused at being left waiting for so long, as Bowie hugs her apologetically.

Yet as the shoot went on, Taylor thawed and Bowie began holding her more and more affectionately. By the end of the day, they looked more like lovers than acquaintances. “With his charm, Bowie could always affect women,” says O’Neill, “and that’s what happened on that day. But Liz never gave him the part in the movie, which I guess was telling.”

‘David showed up stoned out of his head’ … with Liz Taylor in 1975. Photograph: Terry O’Neill/Iconic Images

Bowie was never anything other than interesting, according to O’Neill, who insists that modern pop stars are pampered and manufactured. He believes they’re nowhere near as interesting as the people he was fortunate enough to photograph. When I ask him if he’d be excited to shoot a modern star like Beyoncé, he dismissively replies: “Definitely not. I don’t care about pop stars any more. There’s nobody I want to photograph so I’ve lost interest to be honest. There are no great pop singers like Elton John. The new acts just aren’t as interesting to look at. When Frank Sinatra and all of those guys died, it was awful. It really felt like the end of an era.”

‘I don’t care about pop stars any more’ … Terry O’Neill today. Photograph: Terry O'Neill

He hopes his new book, Bowie by O’Neill, will help a new generation of fans connect with the singer, with the photographs also helping spark memories of a period the photographer admits is now more than a little hazy. O’Neill, who was awarded an honorary fellowship from the Royal Photographic Society back in 2004, sounds genuinely humbled that he’s still being asked to reflect on these photographs.

“At the time, I just carried on taking pictures. When I worked with Frank [Sinatra] he told me to be a fly on the wall and that’s what I was. I never realised that these photos would live on for as long as they did,” he says. “Bowie’s name is going to live on forever and if, by extension, that means my photographs do too, then that’s a really incredible thought.”