Jean Dujardin says George Clooney is a ''locomotive'' on set.

The French actor was amazed by the Hollywood hunk's modesty and passion for his work while shooting WW2 drama 'The Monuments Men', which boasts an cast all-star cast including Cate Blanchett, Matt Damon and Bill Murray.

Asked how he fitted in among the A-list cast, Dujardin told France's TF1 channel: ''By being a clown, it's the best way to bond, humour. But staying awestruck and taking pleasure from the experience and because they're all enjoying it, we communicated that way. You have people who never stop like John Goodman and George, he's like a locomotive. He needs harmony. He's still amazed by his status and his enjoyment of the scenery, the work. He's not blasé. ''

'The Artist' star recalled the first time Clooney contacted him about the film and said the pair have always had a banter-filled friendship because they sent humourous selfies back and forth.

He joked: ''George Clooney sent me an email two years ago, I was in my bathing suit at the time. He said, 'I'm making a film called 'The Monuments Men' and there's a French guy role in it, do you want to come have fun with us?' I sent him back a mail saying, 'It's not possible, leave me alone - I'm on holiday', with a photo attached of me with my hair sticking up everywhere.

''He sent me back one of him with long hair in the 80s so I said, 'OK, you win, I'm coming.' I then told him it was going to take me a good 15 days to understand his script. It's always very easy [working] with George.''