IT was lights, camera, action time.

Anne Hathaway, playing Fantine in the long-awaited movie of the hit musical Les Miserables, was about to sing I Dreamed A Dream, live on camera. The pressure was on, particularly if the Oscar-nominated New Yorker allowed her thoughts to stray to a certain singer from Blackburn, West Lothian. "Anne was quite intimidated by Susan Boyle's iconic version, and I don't blame her," says Tom Hooper, the film's director.

Having made his first musical, Hooper, 40, is also familiar with the notion of feeling the fear but doing something anyway. After The King's Speech, which won four Oscars, including Best Director for Hooper, he faced the question of what to do for an encore. He was sure of one thing: it would be something completely different.

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"I thought 'if there's ever a moment in your life when you can take a risk, this is the moment'. To be conservative, to try to do a similar thing, to try to repeat myself, felt like the wrong thing. I wanted to be as different as I could, to stretch myself, push myself in an area that I don't know about, do something that was going to hopefully make me grow as a filmmaker. The movie musical is about as different as you can get."

Particularly for someone who only got as far as Grade Four on the piano and violin. Hooper's parents encouraged him to learn a couple of instruments, but the youngster eventually gave up. Not even the prospect of leading a chorus of Roll Out The Barrel could dissuade him: "I remember my dad saying, 'But Tom, if you keep going with the piano, you can be that guy when you go down the pub and someone says 'let's have a singsong', you can be the guy who sits down at the piano and knows all the tunes.' I'd say, 'Dad, I'm 12 years old but I already know I'm not that guy. Sorry, dad, I'm just not.'"

But even the little training he had was to prove invaluable when it came time to filming the Olivier and Tony Award-winning tale of redemption, revenge and revolution in 19th-century France. "I cannot tell you how many times on Les Miserables I just thanked God, or thanked my parents, that I did that," he admits, "because music is a language and it started to come back to me. By the end of the process I could read music and read the score. At the beginning I'd completely forgotten how to."

As if it wasn't enough taking on a musical for the first time, Hooper also wanted to defy movie convention. While the traditional method of doing musicals involves actors lip-synching to tracks they have laid down earlier, Hooper wanted them – "them" being Hugh Jackman, Russell Crowe, Hathaway and the rest of the cast – to sing live. It's all about being convincing, he explains. Musicals create an alternative reality, one that is like ours, but one in which people communicate through song. A barrier is immediately set up, one that the audience has to be persuaded to cross.

"My hunch was that one of the things that holds people back from liking movie musicals is lip-synching to playback. However well it's done, you know in your bones there's something not real. The one thing we know all about is the mouth and speaking. We're watching each other speak all the time. We know when something is not real and live, even if it's subconscious, and that creates a barrier between us and the emotions."

A live performance also allowed the actors to "own" the songs, says Hooper, to show the camera the emotions they were feeling in that moment. He had one golden rule for all the actors: "I said they should forget these songs are globally iconic. 'You have to convince me that you have invented this song in this moment and it has never been sung before, and that you've created it.'"

The result, on screen, is a movie musical unlike many of us have seen before - polished, spectacular, but with an edge of rawness. It's the kind of gamble that could make the film remarkable enough to garner awards (it has already been nominated for four Golden Globes) and win over audiences. Hooper has been hard at work on the Oscar circuit already. When we speak in London he has two more trips lined up to Los Angeles before Christmas and one in early January. The Oscar nominations are out on January 15.

ALThough Hooper might have been a newcomer to musicals, he had someone on the team who was anything but a novice. Cameron Mackintosh, producer of Les Miserables, Cats, Miss Saigon, Phantom of the Opera and many other global hits, was a producer on the movie.

The great thing about Mackintosh, says Hooper, was that he adopted an "each to his own" approach when it came to the film. "What I was impressed by was his instinct about when to let me get on with it, when to give me space, when he needed to give me advice. I've never directed a musical before.This is his first film. He knew he knew nothing about filmmaking; I knew I knew nothing about musicals." Where Mackintosh proved essential was, says Hooper, as "a brilliant guide to the DNA of musical construction, why musicals work".

Should Les Mis be nominated, Hooper will at least know what the drill is when it comes to the Oscars on February 24. The story of King George VI and the speech therapist who helped ameliorate the monarch's stammer was one of the biggest British box-office successes of recent times. Made for just $15 million (£9m) it grossed $414m (£257m) worldwide.

Hooper realised the blue touchpaper had been lit at the Telluride Film Festival in Colorado in September 2010 when he was sitting between Colin Firth and Geoffrey Rush in a packed cinema.

"We couldn't believe the number of laughs there were. It was like sitting in a comedy. It got a standing ovation at the end but it was more the expression on people's faces. I thought 'Oh, something has happened here, this film has done something'. Within an hour, if you Googled the film, it had begun. Within a couple of hours I was getting emails from back at home. The word was out."

He's racing to catch a plane to New York for the Les Mis premiere, but there's time to ask him about a previous work, one that won him a fan base among political anoraks everywhere: his HBO series on US president John Adams.

Does he consider any British PM worthy of such lavish small-screen treatment? Mrs Thatcher might have been one, he says, but Phyllida Lloyd got there first with The Iron Lady.

"Churchill is an interesting one because he transitioned such a long journey from the first world war to the second world war. Disraeli is very interesting as well." So that's a possibility, I ask. "I wouldn't say that," he laughs. "I know what will happen. It will become 'Hooper making a musical about Disraeli'."

For his next trick, who knows?

Les Miserables opens on January 11