Derek Jacobi

Sir Derek Jacobi voiced the Master in the animated webcast Scream of the Shalka, played another incarnation of, billed as "Professor Yana", in the Doctor Who episode Utopia, and voiced Martin Bannister and Doctor Who in the Doctor Who Unbound audio drama Deadline.

According to an interview he gave for Doctor Who Confidential, being on Doctor Who was a long term goal of his, ever since the 1960s, as was playing a part on Coronation Street. He has also played Ellis Peters' medieval-detective Brother Cadfael on ITV Television in the 1990s (interestingly, in season 1 the other main character of the series was played by Sean Pertwee, son of Jon Pertwee). Cadfael's role has also been played on radio by Philip Madoc and Glyn Houston.

Behind the scenes
Philip Purser-Hallard said he pictured Derek Jacobi as Claudius whilst writing Of the City of the Saved.... He also pictured Jacobi as Alan Turing, which he said made writing parts where the two were together rather odd.