Eddie Redmayne: From The Theory of Everything to a Thomas the Tank Engine train

The Oscar winner will star as new character Ryan in an upcoming adventure

Eddie Redmayne in the recording studio to voice the character of Ryan in the new Thomas the Tank Engine film (Press handout)

He might have won an Oscar last weekend, but Eddie Redmayne has showed he's not above children's movies by signing on to voice a new train in Thomas the Tank Engine.

The British actor, 33, will star as Ryan in new DVD Sodor's Legend of the Lost Treasure, alongside John Hurt and Jamie Campbell Bower.

Thomas was part of Redmayne's childhood and he "jumped at the opportunity" to be part of it.

"I grew up loving to watch Thomas and his pals getting caught up in unexpected and mischievous adventures," he said.

"I jumped at the opportunity to get involved and what fun it was. I have never voiced an animated character before and I had a complete blast."

Redmayne picked up the Best Actor gong at the Academy Awards on Sunday for his acclaimed portrayal of physicist Stephen Hawking in The Theory of Everything and is preparing to start work on his next film, The Danish Girl.

Reports suggest he is losing weight to play transgender artist Lili Elbe, who was one of the first men to undergo gender reassignment surgery in 1930.

Due out sometime in 2016, director Tom Hooper originally cast Nicole Kidman in the lead but she dropped out after shooting was delayed several times.