William Thomas
From Tardis Wiki, the free Doctor Who reference
William Thomas played Martin in DW: Remembrance of the Daleks, Cleaver in DW: Boom Town and Geraint Cooper in TW: Something Borrowed, TW: The New World, TW: The Categories of Life, TW: The Middle Men, TW: The Gathering and TW: The Blood Line.
He is notable as being the first actor to appear in both the classic and revived series of Doctor Who. Furthermore, he is the only actor to appear in both of those series as well as Torchwood.
