The Sun Online has released an article stating that Life on Mars star John Simm is the "favourite to play" an important character in series 3.
For more details click on the spoiler space below.
The Sun claims that John Simm is in negotiations to play the Master, who would return in a major twist at the end of the third series. Sir Derek Jacobi, 68, will play another Who foe - The Professor. "He poses as a good guy but the Doctor discovers the truth when The Professor dies and regenerates."