As the Man of Steel, he saved the world time and time again; confined to a wheelchair, he became a worldwide advocate for research which could help spinal injury victims walk again. Nick Morrison looks at Superman's two lives.

THE irony was not lost on Christopher Reeve: Superman, the superhero who could leap tall buildings, lift a school bus, and fly so fast he stops the world spinning, was confined to a wheelchair, unable to breathe without a machine's help and told he would never regain movement below his shoulders.

But while others in his position may have been tempted to retreat into obscurity, away from the celebrity limelight and its obsession with perfection, Reeve became a tireless campaigner for more research into spinal injuries, using his fame to open doors and secure funding that would otherwise have been unobtainable.

He harangued presidents on their lack of action; took to the stage at the Oscars to plead for greater understanding of the disabled; set up a foundation to raise money for research, and lent his name to a national centre for paralysis.

But perhaps the most enduring legacy of a man who was paralysed in a riding accident nine years ago came through his advocacy of stem cell research - a controversial technique heavily restricted in the United States - in the hope that it may one day help those who had suffered spinal injuries to walk again, a campaign which saw him mentioned by US presidential candidate John Kerry in his debate with George W Bush on Friday.

The 52-year-old star of the four Superman films died of heart failure on Sunday. He had fallen into a coma after a pressure wound - common for people with limited movement - became infected. For nine years he had fought to regain even tiny movements, astonishing doctors with his progress, but in the end it proved a battle he could not win.

Reeve was a virtual unknown when he was chosen to play Superman in the 1978 film. The son of a novelist and a newspaper reporter, who split when he was a toddler, he was born in New York City in 1952. After studying at Cornell University, he was chosen to study drama at the prestigious Juilliard School in New York, alongside classmate Robin Williams.

He landed a role in the US TV soap Love of Life, and appeared on Broadway alongside Katharine Hepburn, but he had an inauspicious introduction to films, with his first movie role in the critically panned submarine disaster movie Gray Lady Down.

But his transition to global star came when film producers Alexander and Ilya Salkind went to see an off-Broadway production, My Life, early in 1977.

Having bought the film rights for the comic book hero, they were looking for an unknown to play the title role. Reeve screen-tested, and with his thorough preparation and square-jawed good looks, the six foot four inch New Yorker won the role over 200 other actors.

To say it was a career-defining role is something of an understatement. His modesty and his love of adventure - he insisted on doing his own stunts - made him a natural, both as the bumbling Clark Kent and as his caped alter-ego. Starring Marlon Brando and Susannah York as his parents, and Margot Kidder as love interest Lois Lane, Superman was released in 1978 and was an instant hit, going on to spawn three sequels.

Reeve became one of the few stars recognised all over the world, and the total box office of $300m (£167m) made Superman one of the most successful film franchises, but this did not come without a price.

At risk of being typecast, he made a concerted effort to, as he put it, "escape the cape", taking challenging roles as an embittered Vietnam veteran in the play Fifth of July, a time traveller in the 1982 film Somewhere in Time and an aspiring playwright in 1982's Deathtrap, alongside Michael Caine.

It was while filming Superman in London that he met Gae Exton, and although they never married, their relationship lasted several years and they had two children together. After separating from Exton, he met and married Dana Morosinithey, and had another son, Will.

Away from Superman, his film career proved steady but unspectacular during the late 1980s and early 1990s, with appearances in Village of the Damned, The Remains of the Day, The Aviator and Morning Glory.

He became a keen horseman, owning several horses and regularly competing in equestrian events, and it was this passion which saw one chapter in his life virtually brought to a close and launched him into another.

In May 1995, Reeve was competing at Culpeper, Virginia when, after clearing the first two fences, his horse abruptly stopped at the third, throwing him headfirst to the ground.

The top two vertebrae in his neck were fractured and his injuries were so severe he stopped breathing for three minutes. Surgeons had to reattach his head to his spinal column, but they could not prevent Reeve from being paralysed from the neck down. For an action man who loved adventure, it was a shattering blow, and Reeve later admitted he had considered committing suicide, thoughts banished only when he saw his children.

Breathing only with the aid of an oxygen tube, and reliant on others to keep him alive, he was in hospital for seven months, beginning the long rehabilitation process which was to dominate the remainder of his life.

Despite warnings from doctors that he would never be able to move below his shoulders, Reeve refused to give in, and remained dogged in his efforts to recover some movement, however small.

It was a slow process, but the first sign of progress came in 2000 when he moved his little finger for the first time in five years. He later regained the use of a thumb and his wrist, and was able to feel sensations all over his body. In November last year, he revealed that a device had been implanted in his chest to enable him to breathe without a ventilator for several hours at a time.

He also became an indefatigable campaigner for disabled rights. Less than a year after his injury, he went on stage at the 1996 Oscars to make a moving call for more films to be made about social issues; he helped host the Atlanta Paralympics and appeared at the Democratic Party convention the same year; he set up the Christopher Reeve Paralysis Foundation to promote treatments for spinal cord injuries, and the National Health Promotion and Information Centre for People with Paralysis was named the Christopher and Dana Reeve Paralysis Resource Centre.

Reeve also championed research into the use of stem cells - cells which have the capacity to develop into most types of tissue - in the hope they could eventually replace damaged nerves and help those with spinal injuries to walk again.

The work was hugely controversial, with the most effective stem cells considered to be those taken from human embryos, but Reeve's involvement in the debate helped raise the profile of this type of research, as well as of spinal cord injuries themselves.

He also returned to directing and acting, appearing in a 1998 TV remake of Alfred Hitchcock's Rear Window, about a wheelchair-bound man who believes he has witnessed a murder, a performance which won him a Screen Actors Guild Award.

Throughout his nine years in a wheelchair, Reeve was determined not to give up and never abandoned hope, however sceptical the doctors, once saying: "I refuse to allow a disability to determine how I live my life. I don't mean to be reckless, but setting a goal that seems a bit daunting actually is very helpful toward recovery."

And although his role as Superman will live on in celluloid history, it is his role in bringing both attention and research funds to spinal injuries that will be his most enduring legacy. In advocating research which may well give new hope to others, he staked his reputation on an unpopular cause. The tragedy is, it will be too late for Superman.