(Cover) - EN Showbiz - Bradley Cooper says The Hangover: Part II is the hardest film he's ever shot.

The American actor stars in the sequel to the hugely popular 2009 comedy The Hangover. The second instalment of the hit film follows a group of four friends who travel to Thailand for one of their weddings, but things don't go according to plan.

Bradley, who stars alongside Ed Helms, Zach Galifianakis and Justin Bartha in the movie, has revealed that despite the film being full of laughs, filming for the comedy was tough.

"You know what? It was the hardest shoot I've ever done, by far. I mean, The A-Team we shot for six months, I tore my hamstring, I ate nothing but pears and tuna and yet this one was by far the hardest shoot ever, and I don't know why," he explained in an interview with ShortList. "I can't put my finger on it. There weren't blow-ups, but there was a definite sense, a tone and energy of just...It was like walking through mud in a lot of ways."

Bradley has joked that co-star Zach became a diva' after the success of the first film. The 36-year-old says that his fellow actor's grooming regime was far more regimented during the second movie.

"I found it odd that Zach would have a beard-trimmer with him all the time. I didn't like the way he treated her..." he joked. (C) Cover Media