Matt Damon has become the latest victim of George Clooney’s practical jokes on the set of The Monuments Men.

Matt Damon has been working out in the gym every morning before heading to the set of The Monuments Men in order to get in shape for the gruelling hiking scenes in the movie.

Damon’s co-star and long-time friend George Clooney has been having a great time teasing the 42-year-old actor over his fitness regime, so-much-so that he played a trick on him when it came to shooting the hiking scenes.

An on set source revealed: "George got his idea for pranking Matt because he was so damn serious about working out every morning before shooting started.

"Bill Murray and John Goodman kept teasing him but Matt cracked that he'd be laughing when they didn't have stamina for the tough hiking scenes ahead.

''That's all George had to hear. He had the prop guys prepping packs for the hike fill Matt's with solid metal bricks, weighing about 50 pounds. The other guys' packs had lightweight padding but George told them to pretend they felt super heavy.

"By the end of the day Matt was sweating profusely. After the scenes were shot, Matt dropped his pack, opened it and everyone burst out laughing when the metal bricks tumbled out.''

The Monuments Men is currently being filmed in Cambridgeshire, east England.