We have had past Doctors and past companions but David has also worked with a couple of actors who have portrayed the Doctor's enemies too.
Derek Jacobi who portrayed The Master in Utopia with David had previously worked with him in 1998 in the BBC Radio 4 play Hemlock and After.
Terry Molloy, who portrayed Davros from 1984-1988, was in the 2000 BBC Radio 3's production of The Sea by Edward Bond.