Luke Evans has revealed that the thought of acting alongside Jim Broadbent gave him weeks of sleepless nights.
The Welsh actor, who portrays The Great Train Robbery's gang leader Bruce Reynolds, shared screen time opposite Jim as Flying Squad detective Tommy Butler in the BBC show.
"When I was told it was Jim Broadbent playing Tommy Butler, I don't think I slept for a few weeks, because I was so nervous of playing against him," the 34-year-old said before a screening at Bafta.
Luke heaped praise on his Oscar-winning co-star, who is best known for performances in The Iron Lady, Bridget Jones' Diary, Moulin Rouge! and the Harry Potter films.
"It's wonderful. He's a fantastic actor - he's done some incredible roles over the years - and to be able to do this great scene at the end of the second film with him, it was a gift," he continued.
"He's just a lovely man and an incredible actor. I watched and learnt so much from him. I'm part of the new generation of British actors and if I do half the job that Jim has done on screen to make us look so great, I'll be happy."
Luke, who has starred in Fast And Furious 6, Clash Of The Titans and The Three Musketeers on the big screen, admitted portraying someone as charming as Bruce posed less of a challenge than he expected.
"It's so much easier to do this than the vulnerable stuff. It was much easier to inhabit Bruce's character," he explained.
"He's a very clever man and very charismatic. He was always well-dressed and had a way about him. You see him in interviews, as a very calm and collected human being."
The Great Train Robbery, which is split into two stories, will be shown on BBC One in December.