Doctor Who the Blood Cell

"An asteroid in the furthest reaches of space is the most secure prison for the most dangerous of criminals. The Governor is responsible for the worst fraudsters and the cruelest murderers. So he's certainly not impressed by the arrival of the man they're calling the most dangerous criminal in the quadrant. Or, as he prefers to be known, the Doctor. What does impress the Governor is the way the new prisoner immediately sets about trying to escape. And keeps trying. Finally, he sends for the Doctor and asks him why? But the answer surprises even the Governor. And then there's the threat, unless the Governor listens to the Doctor, many people will die."