BBC Spiderman's 33ft leap

He runs up walls, leaps on to narrow ledges hundreds of feet above the street and jumps from rooftop to rooftop. TV viewers this week have been spellbound by a new BBC1 promo showing real-life Spiderman, 28-year-old French athlete David Belle, performing a series of stomach-churning stunts over the rooftops of a busy city.

But in an age where we assume everything is done with computer graphics and sophisticated post-production techniques, every hair-raising leap and fall was performed as seen. There were no safety nets, no mattresses to land on and no second takes. "You see a lot of special effects in commercials these days. This is different, it's real and you feel it," said Tom Ewart of advertising agency Abbott Mead Vickers, which made the film. It is the first on-air promotional film for the BBC's flagship channel.

Although there are no identifiable landmarks, it was shot in London over seven days last month. It shows a man leaving work through his office window and crossing the gridlocked city by leaping over rooftops to get home in time to watch his favourite programme on BBC1.

The opening scenes were shot at the advertising agency's office block in Marylebone Road. The hero, a well-muscled man, is seen finishing work. He then takes off his shirt and climbs out of the window. He apparently defies gravity by climbing backwards up the side of the building wedged between two buttresses in a manoeuvre called The Spider. He reaches the roof and performs a terrifying handstand on a rail eight floors and 120 feet above the traffic.

A forward flip takes him to the top of a multi-storey car park in Poland Street, Soho, where - after a series of jumps and jaw-dropping somersaults - he makes a graceful 23ft dive from one building to another, landing barefoot with a forward roll. It is a trademark move called Manpower.

Although he makes it look simple, one building is seven storeys high (84ft) and the other is five storeys (60ft). He continues in a similar vein, vaulting roofs and leaping buildings in Clerkenwell, until he reaches his flat in time for his programme.

A BBC spokesman said: "It's a way of showing the lengths people will go to to watch BBC1."

The rooftop surfing, however, is part of a new form of urban martial arts currently taking France by storm. Called Le Parkour - the obstacle course - it is a mixture of acrobatics and daredevil antics developed by martial arts expert Belle. Obviously, concentration and grace of movement are crucial. Ross Kirkman, who worked on the shoot, said: "These aren't stunts, they are moves. The shape of the body and the way the arms are held during the leap are absolutely vital."

Belle is currently on retreat in Thailand. He developed his new sport after moving to Paris from the Normandy countryside when he was 10.

Mr Ewart said: "He loved climbing and jumping in the woods. But, when he got to the Evry housing estate in Paris, he suffered real culture shock. So he simply transferred what he had been doing in the country to the town."

He was encouraged in his new hobby by his father, an orphan who had been brought up by the army in Vietnam, which friends say explains Belle's intense self-discipline and interest in the Orient. Le Parkour has made Belle a hero in France and looks set to do the same here. In 14 years, he claims never to have had an accident. But don't try this chez toi.