His roles include the prisoner Morse in the movie Alien 3, Thomas Cromwell in Henry VIII and John Maynard Jefferson in the two part Doctor Who story "The Impossible Planet" and "The Satan Pit" in 2006.
Webb has appeared in many British television programmes, including The Young Indiana Jones Chronicles, Our Friends in the North, A Touch of Frost, Agatha Christie's Poirot, The Bill, Midsomer Murders, Silent Witness and Shackleton.
In 1985, Webb appeared alongside Jon Pertwee in a television adaptation of Karl Wittlinger's Broadway play, Do You Know the Milky Way?
In September 2009, he had a lead role in the BBC1 five-part drama series Land Girls, playing a sergeant in the Home Guard.
He has appeared twice at the Royal Court Theatre, in Chicken Soup with Barley by Arnold Wesker (2011) and The Mistress Contract.