So why on earth do people get Keira confused with other celebrities so much? Perhaps her striking good looks leave fans so star struck they call out the first celebrity name that comes to mind...

Keira, appearing alongside Samuel L Jackson on the Friday night show, also revealed more about her role in new film Begin Again, where her is a guitar-playing songwriter. She asked her musician husband Jamie Righton for help, but "it nearly ended in divorce."

Even Klaxons keyboardist Jamie couldn't help her musical talents, which she admits are limited. "'I like singing if I’m in my own in the shower or if I am really drunk, but I’m not a big fan of singing in front of people, which I didn’t realise until I said yes to the movie and found myself singing in front of rather a lot of people."

So watch out next time you're about to ask 'Britney' for a rendition of Baby One More Time...

Keira Knightley gets mistaken for Britney Spears