ncess Diana as she lay dying in a car wreck in Paris, he told photography students at Stevenson College in Edinburgh.

“It’s not the photographer’s job to editorialise,” said Mr Benson, as he talked about his career last week. “You are not there because you want to be, but because a newspaper wants you there and it’s a hell of a story when the mother of the future king is dating a playboy. That’s a story that had to be covered.” His only criticism of the photographers the night Princess Diana was killed was they didn’t leave fast enough: “They hung around too long.”

Mr Benson was born in Glasgow in 1929. He worked on the Hamil-ton Advertiser and in Fleet Street before heading to America, where he lives in New York. He took up photography, he said, because there were not many alternatives. “Photography was simple,” he explained. “All you had to do was take a good picture. My father wanted me to work in a bank, but I left school at 13 I couldn’t count.”

Mr Benson has photographed John Lennon and his killer, Mark Chapman; he has taken pictures of every American president since Dwight Eisenhower (1953-61); he photographed Elizabeth Taylor before and after her brain surgery; he persuaded Michael Jackson to let him into his bedroom; and Tommy Sheridan to take his top off after he won his defamation action against the News of the World.

Luke Joyce studied photography last year at Stevenson College where students consistently win national and international photography awards and hopes to become a press photographer. He went to hear Mr Benson because “you would be insane not to”, he said. “Any information or advice you can get might help somewhere down the line.”

Luke is in awe of the way Mr Benson was always in the right place at the right time. “He’s amazing if there was a turning point in history, he would pop up round the corner,” he said.

Peter Johnson, 15, is the youngest audience member. He wants to be a wildlife photo- grapher. After listening to Mr Benson, he is even more determined. “You can become a photographer from nothing,” said the Leith Academy pupil. “You don’t have to have a lot all you need is a camera and guts.”

So what was Mr Benson’s advice to budding photographers? Arrive early and leave late, he said. Be original: “I want to show you a picture you’ve not seen before that’s what makes it interesting”; and if you are photographing the rich and famous, do not become star struck. “If you’re given an assignment, you should be thinking about it and not: ‘I’m photographing the president’.”

Mr Benson’s career has not been all glitz and glamour. He photo-graphed the American civil rights movement and has worked in war zones. He took pictures of the pall of smoke above the Twin Towers’ wreckage and of a group of gun weilding vigilantes after Hurricane Katrina had hit. “You’ve got to be prepared.”

Like the night Robert Kennedy was shot. Mr Benson was just yards away when it happened, but he had not planned to go to the Ambassador Hotel in Los Angeles that night. The story was over Kennedy had won the California Democratic presidential primary election but at the last minute, Mr Benson cancelled dinner with friends and went to hear Kennedy’s short victory speech.

“I was going to leave with the crowd, then I thought it would be quicker to go out with Bobby,” he said. “One girl screamed. Bobby was falling down in slow motion. Ethel (his wife) was screaming to give him air. I was getting punched and thrown off balance as I changed film and put it in my sock. Other people were being shot around me five others were shot that day.”

What are his plans for the future, asked one student. To stay alive he’s in his 70s experiment with digital photography, and get a picture of the Pope sitting up in bed reading the sport section of the paper, he answered.