Dame Helen Mirren has moaned her bum looks big in her new movie 'Eye in the Sky'.

Mirren admits it wasn't her favourite costume and she was stressed about what her derrière looked like on the big screen.

During an interview on UK TV show 'This Morning', she said: "I was like, 'Does my bum look big in this? Yes it does!' "

Although Mirren didn't love the clothes she had to don, she was blown away by the attention to detail and the neatness of military uniform.

She added: "The fascinating thing I learnt from the military advisor is that they are obsessed with the detail in a camouflage outfit, like exactly which button is done up, where your hat is, exactly where your belt is, exactly how many rolls of your sleeve you roll up, exactly how your trousers are tucked, they are obsessed with detail. It's extraordinary."

Despite her advanced age, Mirren shows no sign of slowing down in her career and she recently wrapped shooting on 'Collateral Beauty'.

The blonde beauty stars in the movie with Will Smith and a host of other British actresses, Kate Winslet, Keira Knightley and Naomie Harris, and she insists they all had great fun on set with "wonderful" Will.

She said: "I've just finished a film with Will Smith. He's an incredible man, a wonderful man. It's me and all the British girls, I got to wear a mad grey wig. It was me, Keira, Kate and Naomie, all the women in it are Brits, it was amazing."