The world of visual effects has changed immeasurably since London's Double Negative set up shop 10 years ago.

Co-founders Alex Hope, Peter Chiang and Matt Holben had all joined the industry when editing was done on videotape. "It was a world apart from the wonderful things we can do today," says Holben of the mid-1980s, before the digital revolution.

The company was set up in Soho as a unit of PolyGram Filmed Entertainment, with an initial staff of 30 and early credits including Pitch Black and Mission: Impossible II.

There are now 450 employees working on films including Quantum Of Solace, Harry Potter And The Half-Blood Prince, Prince Of Persia: The Sands Of Time, The Boat That Rocked and Green Zone.

Universal formerly had a minority shareholding but now the company is 100% privately owned by Holben, Hope, Chiang, Paul Riddle, Paul Franklin and Charlie Noble. "In essence, we've been masters of our own destiny since then," says Hope. "What we've seen since 2002 is that the company has grown year on year. Staffing levels, turnover, quantity and quality of work has grown."

He adds the company is now capable of undertaking "multiple large projects". In recent months, Double Negative was busy with "a significant proportion" of the work on The Dark Knight while handling all the visual effects on Hellboy II: The Golden Army and contributing to the latest James Bond and Harry Potter movies.

The challenge for Double Negative has been to achieve what Hope calls "sustainable growth". The founders do not want to expand quickly when business is booming and then have to contract suddenly if there is a downturn. "We don't get into the rollercoaster of hiring and firing," Hope says.

To outsiders, the cordial relations between the major London effects houses may seem surprising. Surely, Double Negative is competing ferociously for business with the likes of Soho neighbours Cinesite, the Moving Picture Company and Framestore.

"We have a fantastic relationship with the other companies," Chiang says. "It's a reflection of how well we work together that most American blockbusters (using London's visual-effects houses) are split between three or four companies. It's that sort of relationship that has allowed the industry to grow without one company having an almighty monopoly."

"London has to be a centre of excellence and a viable commodity for the Hollywood studios," adds Hope of the camaraderie in London's visual-effects world. "We have to show London is big enough to handle multiple films and so the studios are happy to bring the work here."

Further afield, Double Negative has a joint venture with Cube, a team of artists in Hungary. The outfits collaborated on some of the work on Hellboy II.

"We see that as a signpost for the way forward," says Hope. "It allows us on a show like Hellboy to produce the best possible work at the right money."

Hope acknowledges it has been "a peculiar year" thanks to the writers' strike in Hollywood, the threat of the actors' strike and the turbulent financial markets. "We could see the problems that were going to arise from the strike and we've made real efforts to ensure we have enough of the right work coming in."

"It's about being able to structure yourself so you can deliver the best possible work for the right money," Hope declares. "That's not about discounting. For us, it's all about the artists - the quality of the talent and how those teams are managed."