Ah, Dan Starkey... Doing a bit of brief research, I see he played Skorr in the Sontaran two-parter; he was Jask (not to be confused with the Cult of Skaro member) in "The End of Time"; and, of course, the afore mentioned Strax. Hmm, he's actually tied with Kevin Lindsay for the number of Sontaran characters portrayed. (Remember, Lindsay played both Styre and his Marshall who appeared on a video relay.) Even Chris Ryan has played only two, General Staal and later Commander Stark.