Marion Cotillard had eight dresses to shoot one sex scene in 'Allied'.

Costume designer Joanna Johnston felt it was important to keep the actress and her co-star Brad Pitt's outfits ''simple'' when it came to their outfits before they got intimate, and admitted there needs to be a lot of ''repetition'' as the garments get ripped.

She said: ''I wanted to keep their clothes very simple--and in fact they're both in pale colours. I didn't want there to be a distraction with their clothing.

''She had a detail of beautiful drawn thread-work on her dress, and underneath it there were layers of underwear to peel off in pale peach silk satin. The action was in the forefront of my mind in this design.''

''There's a lot of repetition in a lot of the outfits. The long green dress, we made eight of those.

''There's much more repetition that you imagine, but yes, the sandstorm scene we had repeats--they wore white, so we had to back ourselves up!''

Joanna felt very attached to all the outfits in the World War II drama but admitted her favourite changes all the time.

She told ''Every time you create something, you have a bit of a crush on that piece. One of Brad Pitt's heavy Irish linen suits, I had a crush on the fabric.

''And Marion's dressing gown on the rooftop--I loved the fabric. If you ask me the same question over a 10-year period, I'd answer a different way each time!''

Though the early part of the two stars' on-screen courtship largely takes place on a roof with both in their nightwear, Joanna was conscious of trying to make both Marion and Brad look as ''sexy'' as possible.

She said: ''The rooftop scenes were very evocative - you had to feel the heat. I wanted them both to look really sexy.

''I wanted Cotillard to be classically sexy, so she's in a silk-satin nightdress with lace. And then the robe - I wanted air to move in it - so it was very breezy. I used a very light-weight silk.''