George Clooney didn't have time to play pranks while filming 'The Monuments Men'.

The 52-year-old actor stars as Lieutenant Frank Stokes in the action drama which he also produced and directed, and because of the intensity of his involvement in the film he didn't have time to mess around with most of the A-List cast, but he made an exception for co-star Matt Damon.

Bob Balaban - who stars as Private Preston Savitz alongside the Hollywood legend - told BANG Showbiz at the movie's UK premiere at the Odeon in London's Leicester Square on Tuesday night (11.02.14): ''George doesn't have time to play pranks when he's directing and acting in the movie - I don't know how he had time to eat - but he did do one, he pranked Matt Damon. But none of the rest of us had the pleasure of getting embarrassed.''

Balaban praised Clooney for his attitude on set and dedication to the film which is based on the true story of a team of soldiers who recovered millions of pieces of artwork stolen by the Nazis in WWII.

He added: ''I found him [George] wonderfully self-effacing and interested in doing his job.''

Bill Murray, John Goodman, Jean Dujardin and Hugh Bonneville were among the other stars to attend the premiere.