The state-of-the-art film and television studios are set on a 200-acre site and include huge sound stages, one of the largest heated underwater filming tanks in Europe and a 100-acre "clear horizon" back-lot for outdoor scenes.

Warner Bros Studios Leavesden, where much of the eight-film Harry Potter series was shot, goes head-to-head with other major British facilities, including Pinewood Studios located just a few miles away.

The investment by the Time Warner Inc-owned Hollywood studio, which acquired Leavesden in 2010, has been seen as a vote of confidence in British film-making at a time of economic uncertainty in across Europe.

"We have confidence in the future of the British film industry and the production business generally, and we intend to continue to make movies and TV shows here," said Josh Berger, president of Warner Bros UK, Ireland and Spain.

"We're coming off a very strong period for British film - global blockbusters made alongside smaller but incredibly successful films," he told Reuters.

"There is no reason to think that that should change dramatically in the future and our investment in Leavesden is another of those reasons to be bullish."

In addition to Harry Potter, a record-breaking franchise which grossed $7.7 billion in global ticket sales, Warner Bros has filmed "Sherlock Holmes", "Charlie and the Chocolate Factory" and "Wrath of the Titans" at Leavesden.

The facility, which can handle two blockbusters shooting at the same time, is the only one in Britain to be owned and operated by a major Hollywood studio and is one-and-a-half times the size of Warner's studios in Burbank, Los Angeles.

It will be available to rival film production companies, as well as for television shows and music videos.

On the movie side, Warner has enjoyed huge success in Britain in recent years, and in 2011 topped the national box office rankings with ticket sales of 206 million pounds or an 18 percent market share.

It is also a major player in television in Britain, particularly through its majority stake in Shed Media which makes hit reality TV shows "The Voice" and "Supernanny".

Berger said Warner would make an announcement in the near future about its first deal at the refurbished facility, but declined to give any more details.

The new Leavesden Studios are adjacent to Warner's recently opened Harry Potter tour which the company hopes will be a major visitor attraction for fans wanting to experience the original sets, costumes, special effects and animatronics.

(Reporting by Mike Collett-White, editing by Paul Casciato)

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