And the English Patient actor wasn't the only hunk Keira was mingling with at the do. The evening marked a rare couples' outing for the screen siren and her actor beau Rupert Friend, too. Fresh from a holiday in Indonesia, the pair - whose romance blossomed after they met on the set of Pride And Prejudice - showed they're as in-tune as ever by colour-coordinating their outfits.
In the flick Keira plays Georgiana Spencer, an aristocrat who becomes trapped in a loveless marriage with the Duke of Devonshire - played by Ralph - who is desperate for a son. And while the Pirates Of The Caribbean beauty says Georgiana - a distant relative of Princess Diana - was a "very exciting character to play", there were aspects of filming she wasn't quite so keen on.
"I had to be sewn in each time I put a costume on… That was what happened in those days," reveals the 23-year-old, who spent two hours dressing for her role every day. "While the end results would have been a fabulous look, getting there wasn't easy.
"The clothes, the wigs and the hats were so heavy that it became painful to stand around. At one point I had to wear a wig that was two feet high and the weight pushed my head down into my neck. The camera couldn't even see my eyes!"