'Pubescent boy' Keira Knightley

Jun 17, 2008, 12:00 GMT

02/10/2008 - Keira Knightley - The Orange British Academy of Film and Television Arts Awards 2008 (BAFTA) - Outside Arrivals - Royal Opera House - London, England © Solarpix / PR Photos

Keira Knightley sounded like a "pubescent boy" when she sang in her new movie.

The 23-year-old actress - who plays Dylan Thomas' lover Vera Phillips in 'The Edge of Love' - was "terrified" when director John Maybury ordered her to sing live, because she believed she would be miming to a pre-recorded track.

She told BANG Showbiz: "I went to voice coaching. I was absolutely terrified. I thought my legs were going to buckle and on the first couple of takes I sounded like a pubescent boy! I didn't realise I was going to have to do it live.

"I did go to a studio and record it beforehand so I thought when I got there I would just be miming and then on the morning when there was god knows how many extras and hundreds of crew members John came to me and said I had to do it live. I have never been more terrified in my entire life! But actually, it was fun in the end."

Meanwhile, Keira's mother Sharman Macdonald - who wrote the film - has revealed she only included the singing as revenge for Keira choosing to play Vera instead of Caitlin MacNamara, a role Sharman originally wrote for her daughter.

Sharman said: "When Keira set up meetings in Los Angeles to discuss the film, they asked her if she would be in it. Then when she spoke to me next and told me she was going to play Vera, and not Caitlin, I thought, 'Right! I'm going to put singing in it!' "