Taylor Swift has confirmed 'I Knew You Were Trouble' was written about her ex--boyfriend Harry Styles.

The 23-year-old pop star gave a scintillating rendition of the song at the ceremony in February as the One Direction heartthrob looked on, and she found it easy to connect with her emotions as the person she wrote it about was so close to her.

Taylor - who ripped off a conservative white wedding dress and gyrated on stage in a sexy black and lace outfit at the BRITs - said: ''Well, it's not hard to access that emotion when the person the song is directed at is standing by the side of the stage watching ... You're balancing the analytical side of your brain which is telling you where to go and how to go there, with the other side of your brain, which is saying, 'Feel everything you're singing, and show it on your face. Feel everything exactly as you felt it when you wrote the song.' ''

Taylor - who has written tracks about several of her famous former lovers, including John Mayer and Jake Gyllenhaal - insists she no longer has time for guys who are scared of commitment and she can't understand why some men change when they are in a relationship.

In an interview with The Times Magazine, she said: ''There's really no sound quite as loud as a phone not ringing, a letter unanswered. I don't quite understand it, because I either want to be with you or I don't ... I really don't feel like pursuing something that isn't real or isn't going somewhere, so if it's established that someone's commitment-phobic, I'm sorry - go be commitment-phobic with someone else. Because I'm not trying to scare you, I'm not pointing a gun at you; I'm offering to be with you.''