ACTOR Jude Law claims he got to steer a nuclear submarine after being allowed on board for a four-day stint to prepare for a forthcoming movie role.

The star said he is allowed to reveal very little about the experience because it is "top secret", but admitted he reeked after his spell underwater.

Law, speaking on tomorrow's Graham Norton Show on BBC1, said he was allowed on the sub to research his performance in the film Black Sea.

He said: "I'm not sure how much I'm allowed to say because it was a proper nuclear sub and top secret. I'm not sure it helped me to be honest, but it was an amazing experience. We spent four days on board and they just let me wander around, and I steered it for a bit."

Law said he coped with the confined space but had difficulties with being crammed in so close to his fellow submariners.

"For me it was more about the proximity of other people. You hot-bunk with other people and the commander said with such joy, 'You're going to smell like a badger when you get off'. And he was right, I did," he said.

While working on the film he said the cramped conditions meant the actors had to express themselves through moving their backs because they spent so long facing away from the cameras.

"You're limited and an awful lot of the footage is shot over a shoulder, so we came up with 'backing' - who could act the best from behind," he said.

"It became a running gag and we started giving awards for the best."

The interview will be screened during the chat show which is screened at 10.35pm tomorrow.