In a photojournalism career spanning more than half a century, Harry Benson has covered it all.

He has photographed every US president since Eisenhower, covered wars in Afghanistan and the Middle East and captured intimate, unforgettable portraits of a legion of movie stars and icons of the 20th century.

He was just yards away when Robert Kennedy was assassinated at the Ambassador Hotel in 1968. He was on hand to watch as the Berlin Wall went up, and he was there again when it came tumbling down.

But it was the 1964 photo of a pillow fight involving four young musicians from Liverpool that changed Benson's life forever.

The Scottish photographer's iconic image of The Beatles scrapping playfully in their Paris hotel room -- moments after being told they had reached No.1 in the US charts -- remains Benson's favorite from a life's work that is the subject of a major retrospective at Los Angeles' Pacific Design Center.

"I like it because it's a happy picture," Benson told AFP. "And it meant I was coming to America. It changed my life. And I honestly think it was the best picture ever taken of The Beatles.

"There is an innocence about it, a naivety. It was before drugs, before cynicism. It reflected the times, the optimism of the early 1960s."

Ironically Benson, who turns 80 next year, was initially reluctant to photograph rock stars. His employers, The Daily Express newspaper, had ordered him to Paris with The Beatles on the eve of a long-planned trip to Kenya.

"I was desperate to go to Kenya, I wanted to do a serious story. The night before I was supposed to leave I got a call from the picture desk saying 'We'd like you to go to Paris with The Beatles'," he recalled.

"I explained that I'd had all my shots and was ready to go to Africa in the morning and managed to talk them out of it. Five minutes later the phone rang and I was told 'The editor says you're going to Paris.' So that was that."

Paris, he remembers, was "cold and miserable". But then he saw them play.

"And from the very first song I knew, honest to Christ, that I was on the right story. The music was so good. It lifted you right up, the crowd roared. You could see Beatle-mania happening right before your eyes," he said.

The famous photo of the pillow fight was captured in the George V Hotel in Paris, shortly after manager Brian Epstein had walked into their suite with a telegram informing them that "I Wanna Hold Your Hand" had reached No.1.

"I had been with the group a few nights before and they'd mentioned a pillow fight and I thought it would be great to recreate it. But a rival photographer was there and I didn't want him to get the same shot.

"So a few nights later, after a show the group were drinking. When Brian Epstein came in and told them about the No.1 they were so happy, so I suggested a pillow fight and they said 'Okay.'

"But John Lennon said, 'No, we'll look childish.' And Paul (McCartney) said 'I agree'. But then John slipped away and a few moments later came back and smacked Paul with a pillow as he was having a drink.

"And that just started the pillow fight. All hell broke loose."

From Paris, Benson traveled with The Beatles to the United States, and once stateside the Glaswegian never left, quickly finding work with Life magazine and starting a lifelong love affair with America.

Based in New York, Benson chronicled the cultural maelstrom of the 1960s, most dramatically in 1968 when he was on the scene at Bobby Kennedy's murder in Los Angeles.

"I turned around and there was a girl with a straw boater on and she screamed. And there was Bobby, just falling to the floor in slow motion," Benson recalled. "And I remember thinking 'This is what you came in the business for. Don't fail. Mess up tomorrow but not today.'"

Benson's images from the chaos that ensued include an unforgettable photo of Ethel Kennedy, hand outreached as she screams for help.

"I basically tried to photograph everything I could see. That's what journalism should be. What you see should inform," he said.

Politicians have been a constant source of work for Benson, who is currently under contract to Vanity Fair magazine, and who regularly works for Architectural Digest, Newsweek and The Sunday Times.

He says the most candid pictures are usually those taken early in politicians' careers, citing a photo of Bill and Hillary Clinton embracing on a hammock in Little Rock, Arkansas, in 1992 shortly before the election campaign that would send Bill Clinton to the White House.

"It was a pleasant afternoon in Little Rock and I mentioned the hammock to Bill so he sat on it," Benson said.

"I asked Hillary to join Bill and give him a kiss, and she laughed and said that she'd come into politics to be serious.

"But that picture would never happen again. They would never do that. Not because of anything being different between them.

"It's just that everything was new then, and there's a time when things are new that you can get a lot more. Once people have been around, they're instinctively more wary."

As someone who has covered his fair share of celebrities, Benson has mixed feelings about the bad press received by modern-day paparazzi who swarm around the likes of Britney Spears.

"I think paparazzi keep their image alive," he says. "But if I was an agent I would be telling my clients to go to the supermarket and look your best.

"Because the pictures taken of them when they're at the supermarket shopping are often better than the ones of them walking down the red carpet at the Academy Awards, where they often look hideous.

"Celebrities should take advantage of it and let the paparazzi enjoy themselves."