To say that the Doctor's relationship with the Master is turbulent would be the understatement of the century but every now and then something happens that brings it one step closer to making some sort of sense. The Tenth Doctor broke the Whovian heart(s) of the entire nation at the end of the climactic Series 3 finale as he desperately begged his arch-nemesis to regenerate. The Master won in the end, making our honourable hero the last of the Time Lords once more. Gutted.