ONE morning early in 1955 Phil Stern, a photographer with Lifemagazine in Los Angeles, was driving to his office on Sunset Boulevard. "As I was passing the junction with Crescent Heights, this crazy bastard came through the red light on a motorcycle, " he tells me, now in his 80s. "We both screeched on our brakes.

As he got up off his bike, I recognised him. I'd come very close to killing James Dean."

They ended up having breakfast at Schwab's drugstore.

Dean's first movie, East of Eden, was about to come out. His bad boy 'live fast, die young' reputation had already turned him into a youth hero in conservative McCarthyite America. "He was hell-bent on self-destruction, " recalls Stern, "and in that he was to be successful." Stern was supposed to be taking shots of Marlon Brando and Frank Sinatra on the set of Guys and Dolls in Goldwyn studios. When they didn't show up, he photographed Dean instead. His iconic image of Dean with his eyes peering over the top of a dark turtleneck sweater . . . and another of him sitting back with his legs up on a table . . . would help immortalise the 24-year-old actor when he died in the twisted wreckage of his silver Porsche Spyder six months later.

"It made a rich man of me, " says Stern. "It put my four grandchildren through college. I wish I could tell you that it was all my creativity, but I didn't do a damn thing. He did it. The sweater was his idea. All I did was click. Dean made the style, not me. He wanted to be documented. He knew what made a good image. Most actors do. They can see what it's going to look like."

Now 50 years on, Dean is not just the archetypal rebel for every cause, he has . . . since the CMG agency took control of his image in 1984 . . . become a hugely bankable franchise. The official James Dean website has registered over 130 million hits since it was launched in 2000. Last weekend, fans from all over the world flocked to Dean's home town of Marion, Indiana for screenings of his three movies East of Eden, Rebel Without A Cause and Giant on a 100ft screen at "the world's largest digital drive-in theatre". The movies have just been released globally on DVD by Warners, together with a documentary, James Dean: Forever Young, which premiered at Cannes last month.

"Right after Jimmy's death, we started getting a lot of fans coming to the house, " says Dean's cousin, Marcus Winslow. "I know at the time everyone thought after three or four years it will all die down. But it really didn't turn out that way.

Amazing as it is, Jimmy just keeps getting new fans all the time.

I'm just a farmer. I never dreamed that I'd be here in Cannes one day talking about him."

He's sitting with me in the bar of the Carlton Hotel. He was only 11 when Dean died. "My memories are probably different to most people, " he says. "Jimmy came to live in our home after his mother died three years before I was born. He's just someone that I remember always being there, I suppose like an older brother. I remember him going to school on a motorcycle my dad had bought for him. He used take me riding on it.

"There was an ice-cream store about a mile down the road called the Dutch Mill, because that's what it looked like. I'd straddle the fuel tank. You could just ride up to the front counter.

You didn't have to get off the motorcycle to get an ice-cream cone. When Jimmy went away to California after he graduated from high school, my sister gave a going-away party for him one Sunday, a kind of surprise party. I can remember going to that."

Dean came back to visit regularly, even when he was in New York and later Hollywood. "He got to do a lot of TV shows, which I watched, " says Marcus. "He used write letters with little sketches. He was always encouraging me to draw pictures.

I drew a castle, which I thought was pretty neat. It had turrets and all that stuff. He sent me a letter right back. He felt castles were things of confinement. He said it's better to draw things that are free, like animals and trees and mountains, things that were created by God. Of course I understand that now more than I did at the time. It's kind of touching to read those letters."

Marcus's parents were driving back from a visit to Dean in LA the night he died. "I had to stay home and go to school. So I was with my sister. Jimmy's dad called her and told her what had happened. It was pretty late. I was already in bed. I didn't find out until first thing Saturday morning. All I knew was that someone had turned in front of his car. He's buried only about a mile from the farm, half way to Fairmount. My parents are on one side of him and his father and mother are on the other. Pretty near every day when I drive to town I see some car there at the grave."

Some months before, he'd watched Dean's debut in East of Eden as a wayward youth at odds with his father and looking for his lost mother. "It just didn't seem like he was acting, " he says. "It just seemed like Jimmy. The way he walked with a slouch, his head to one side, the kind of giggle he had. Hell, it's not acting. It's just him. I guess that's probably always been my favourite. Rebel Without A Cause and Giant hadn't come out when he died, but there was just something about seeing them and knowing that he wasn't with us any more, a kind of sadness that hung in the air. Of course you look at them a little differently now. But I know at the time it was really hard to watch."

Humphrey Bogart claimed that what made Dean different was that he died at the right time. "He left behind a legend, " Bogart said. "If he had lived, he'd never have been able to live up to his publicity."

His biographer George Perry disagrees. "You may feel there are a lot of actors like him today, but there weren't then, " he tells me. "He very much went against the grain of what acting was. Marlon Brando and Montgomery Clift had come before him. He idolised both of them. But he was different from both of them. He brought a kind of energy and freshness and danger to acting that simply hadn't been there before."

Dean had barely started when everything ended. If he was alive today he'd be the same age as Clint Eastwood. Paul Newman became a star in the roles of Rocky Graziano in Somebody Up There Likes Me and Billy the Kid in The Left-Handed Gun that Dean was to have played. Bizarre myths proliferated. Dean's father Winton allegedly abandoned him when his mother Mildred died of cancer at 29, sending him back to Indiana in a train with her coffin instead of raising him in Santa Monica, a shattering experience that gave a desperate intensity to his performances as a son who cannot get his father to love him in East of Eden and in Rebel Without a Cause. "There was no estrangement, " says Perry. "He had a loving relationship with his father right up to the end. You can see this from piles of letters Marcus still has."

It would be more accurate to say that . . . like Cal in East of Eden . . . Dean never got over the loss of his mother. "I think he picked the acting up from her, " says Winslow. "Of course, I never knew her, but they say she could impersonate and you just knew right away who she was impersonating. She used make plays with him with little dolls, performed on a cardboard stage."

Germaine Greer recently claimed that Dean was "queer as a coot" and that his behaviour was driven by an "unslaked need for transgressive sex". No one who knew Dean accepts this.

"My guess is that he could have been both ways, what we call AC/DC, " says Stern. "He nearly married Pier Angeli, but her mother insisted that she marry Vic Damone, a nice Catholic Italian boy. Jimmy was very cut up."

"I think because he was an actor, he had a kind of mission to encompass all human experience, so he may have experimented sexually, " says Perry. "You must remember he was only 24."

Marcus Winslow was too young to know what homosexuality was. "I think Jimmy liked to be around all kinds of people, " he says. "But I don't think he was like that. Believe what you want to believe, I guess."