Johnny Depp and Paul Bettany worked out naked together to get in shape for 'Mortdecai'.

Speaking at a London press conference to promote the motion picture, Paul quipped: "We worked out together every morning. Naked."

Johnny said: "We did our jazzersize. In legwarmers."

Paul joked: "That was it. In legwarmers and nothing else."

Johnny also found it particularly funny when Paul's character Jock Strapp was set on fire in the movie, joking it was the "best day of his life" seeing his co-star's reaction when he was getting readied to be set alight.

Johnny said: "I watched him on fire, he was on fire. He made me laugh, sorry."

Paul added: "I think one of the things that led [director] David Koepp to put me in the movie was that he likes to see me in precarious situations I've noticed throughout the years."

Johnny said: "In those situations that might be somewhat harrowing, when you see that truth, that real honest reaction, that kills me.

"To see him anticipating being lit on a fire was the best day of my life. It was the funniest thing in the world."

Paul explained: "I remember they were putting this petroleum jelly on me and I just remember staring at Johnny the whole time and shaking my head.

"Johnny laughs at everybody hurting themselves, except for his children, including himself."