Christian Bale had to shift weight for Ford v Ferrari

The 45-year-old actor plays racing driver Ken Miles in the film, which tells the true story of the battle between Ford and Ferrari at the 1966 24 Hours of Le Mans race, but he soon realised he would have to shift some pounds because he couldn't get inside the vehicles from that decade.

Christian told Variety: "I had to get in the car. I could not bloody ... these things are not made for comfort, these cars. They're tight. So, I couldn't bloody get in them. That would have been a whole different film."

The problem was made worse for Bale as he had to gain 40 pounds to portray Dick Cheney in 'Vice' in previous role.

Bale has bulked up and slimmed down for many of his big screen roles, including adding muscle to his frame to be Batman in 'The Dark Knight' trilogy and shifting 62 pounds to play paranoid insomniac Trevor Reznik in thriller 'The Machinist'.

Bale he had a "great deal of fun" playing Miles, who died just two months after competing in the race.

He said: "He was an easy character to channel intensity into, but a great deal of fun as well. He was a guy who really enjoyed his life. He loved what he did. That's why he was so passionate and despised the bureaucrats who would come along and spoil all the fun, basically. He just thought there was no room for them in racing."

Ford v Ferrari also stars Matt Damon, 49, who plays car designer Carroll Shelby.

The 'Jason Bourne' star opened up on how he watched actual footage of Shelby to prepare for the role.

He said: "I watched a lot of footage of him to try to get a sense of how to do it. You just try to get the essence of the person, so that people who remember him go, 'Yeah, you're in the neighbourhood.' Then just try to tell the story as best you can."