It made its director, George Lucas, a billionaire. Harrison Ford (Han Solo) went on to become, well, Harrison Ford, the megastar whose movies have earned more than any other star's. Alec Guinness (Obi-Wan Kenobi), of course, had as illustrious a career post-Star Wars as before it. Even Carrie Fisher (Princess Leia), after Hollywood's obligatory cocaine and alcohol detour, resurrected herself as an occasional actress but a more successful novelist and screenwriter.

But what became of Mark Hamill, who played Luke Skywalker? Twenty years ago, the young, wholesomely good-looking Hamill was tipped to become the biggest star of them all. It never happened. People who press him about it tend to get their heads snapped off. "So why aren't I Harrison Ford?" he barked at a reporter from the San Francisco Chronicle. "I don't know - I'm not. After Star Wars I guess I tried to establish normalcy. After something becomes a pop phenomenon like that, you want to reassure yourself that you haven't really changed."

Hamill has never turned up at any of the Star Wars conventions over the years. Indeed, until he ventured, uneasily, to the LA premiere of Star Wars recently, he had not seen any of the films since they were first released. He never watched them on video.

Hamill has always denied that his career was affected by his near-fatal 1977 car crash, which resulted in extensive reconstructive plastic surgery to his face. Or by a period of self-destructiveness. "I would imagine I went through a phase many people my age went through, where drugs and alcohol were a part of their lives, but that's long gone," he said.

For a long time, however, Hamill could not get arrested in Hollywood. He decamped to New York in the 1980s, taking barely glamorous roles in The Nerd, The Elephant Man and a touring production of Amadeus. Returning to Hollywood, he ended up in films that few people, thankfully, saw, such as Midnight Rider and John Carpenter's remake of Village of the Damned.

Meanwhile, the star of the biggest movie of all time fell back on cartoon voiceovers - he voiced the Joker in Batman: Mask of the Phantasm. More lucrative have been two Wing Commander CD-Rom games. Hamill has also co-written a comic-book thriller, The Black Pearl, which he hopes to turn into a film.

Hamill would not want anyone to pity him. He lives in Malibu, he has a fan club, there is a Mark Hamill site on the Internet, and he will always be financially secure on Star Wars royalties. Now 44, he has maintained a 19-year marriage. And he has three children, who have suddenly come to appreciate that Dad is one of the biggest movie stars in history.

Perhaps Hamill will eventually realise that the Force has been with him all along.