Christian Griswold

 was a criminal locked up in the same cell as the Eighth Doctor. He was the person the Doctor and Charley saw pulling a gun on Christian de Roche. He was annoyed that the Doctor had stopped his assassination attempt. He escaped using one of the Doctor's keys. He later threatened Georgina Marlow to get money out of her and the Doctor to pay after the botched assassination attempt. (AUDIO: Other Lives)