Veteran English actor SIR Derek Jacobi will star in the third series of hit BBC show Doctor Who. It's not yet known what role the famed thespian will play - but British newspaper the Daily Mirror claims the 68-year-old will take on the role of THE PROFESSOR, a "good guy" who takes a "key role in preventing the world from ending". It's not the first Doctor Who encounter for Jacobi - he appeared as renegade time lord The Master in an online version of the sci-fi series in 2003.