He is the master of the intelligent Hollywood action film who graduated from British television to make two of the biggest box office hits of recent years and earn an Oscar nomination for his film about the September 11 attacks.

Now Paul Greengrass, director of The Bourne Supremacy, the Bourne Ultimatum and United 93, has revealed the unlikely source of his inspiration: the video-sharing website YouTube.

“If you look at YouTube it’s packed full of film-making,” he said after an appearance at The Times BFI 51st London Film Festival this week. “I look at it all the time, at how people manipulate images in a fresh way. There’s a vibrancy and a wit and a sense of attack online.” YouTube has become one of the most visited sites on the internet since it was founded in 2005, prompting Google to pay $1.65 billion for it last year. However, where most of the site’s vast fanbase see an anarchic blend of TV bloopers, sports highlights, amateur video diaries, comedy sketches, concert bootlegs and overnight cult heroes, Greengrass sees a home for cutting-edge craftsmanship.

His own distinctive, visceral shooting style, forged making television docudramas such as Bloody Sunday and The Murder of Stephen Lawrence, has become more extreme as a result.

“It’s the pace of them. Why do you think people accept the level of kinetic violence in the Bourne films? It’s because that’s how images are now.”

Greengrass was astonished by the speed, flair and professionalism of the new generation of guerrilla film-makers that he encountered while filming the climactic car-chase sequence for The Bourne Ultimatum in New York.

“After ten days or so there were pictures up on YouTube. People had been shooting our car chase with their mobiles, cutting it together and putting it to music. I would go: ‘Christ, that’s better than what we’ve done’,” he joked. “That’s definitely the way that film-making is heading.”

At 52, Greengrass, has established himself as one of the world’s most sought-after film-makers since shooting his Hollywood debut, The Bourne Supremacy, in 2004. His career hit a new critical and commercial peak this summer with his second film in the trilogy, which has dominated the global box office. Even the jaded critic from Variety, the industry magazine, was moved to say: “If they could bottle what gives The Bourne Ultimatum its rush, it would probably be illegal.”

Greengrass belongs to a group of British directors who cut their teeth in television before going on to achieve big screen acclaim, along with Joe Wright and David Yates. Previous finishing schools for British talent have included the theatre and advertising. The next wave will come from the internet, he believes.

“Out of this unbelievably fertile ecology you will get new film-makers coming up,” he said. “There’s wonderful work being done online.”

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