He and Brother Theodore have both played Gollum twice. Theodore played the role in The Hobbit (1977) (TV), while Woodthorpe played him in The Lord of the Rings (1978). This incomplete adaptation sparked two other adaptations: the animated The Return of the King (1980) (TV), in which Theodore reprised the role; and the BBC radio production, in which Woodthorpe reprised the role. Theodore played the role opposite Orson Bean, who played Frodo, but had previously played Bilbo in The Hobbit. Woodthorpe played the role opposite Ian Holm, who played Frodo, and would go on to play Bilbo in Peter Jackson's films.
Played Gollum in both The Lord of the Rings (1978) as well as in the Lord of the Rings BBC radio production.