Sophia Myles played Jeanne-Antoinette Poisson in the Doctor Who television story The Girl in the Fireplace. She later played Rania Chuma in the Fourth Doctor Adventures audio stories Kill the Doctor! and The Age of Sutekh.
Prior to her appearance on Doctor Who, she was best known for appearing in costume dramas: she appeared in Underworld and as Lady Penelope in the remake of Thunderbirds, along with Ron Cook as Penelope's Driver, Parker. Myles also starred as Isolde in Tristan + Isolde and as Kate Breck in Hallam Foe.
Before she starred in Doctor Who, she was romantically involved with her The Life and Adventures of Nicholas Nickleby co-star Charles Dance, thirty-four years her senior.
During filming of The Girl in the Fireplace, she began dating David Tennant. During this period, she assisted the Doctor Who production crew by reading the role of Donna Noble at the 29 June cast read-through for The Runaway Bride (Catherine Tate was not available). She also helped Tennant record some of his video diaries for the DVD box sets, appeared in a couple of them and also handled the camera.
Like Tennant, she also appeared in an episode of Extras.
She also contributed to the charity reference book Behind the Sofa: Celebrity Memories of Doctor Who