He is known for portraying Dickon Sowerby in 1993 film adaptation The Secret Garden, based on the novel by Frances Hodgson Burnett, and as Henry Green in the television drama series Where the Heart Is.
Knott's first major film was Warner Brothers' The Secret Garden in 1993, in which he played Dickon Sowerby.
In the late 1990s, he played Darren Featherstone and Liam Shepherd in Coronation Street.
The National Theatre production later toured the world, affording Knott his Broadway debut.
He reprised his role on BBC radio, and in Bennett's film adaptation which was directed by the National's Nicholas Hytner.