Alistair (The Time of Angels)

 was an acquaintance of Doctor River Song, with whom he had danced in the past (DW: The Time of Angels). He came to the conclusion that River was onboard his ship, the Byzantium when he discovered one of his guards with hallucinogenic lipstick on his cheek. When he encountered River, Alistair intended to have his guards kill River and make it look like she was trying to escape, but she delayed by predicting that the ship would not arrive at its destination. This allowed an airlock door to open into space, expelling her to be rescued by the Doctor in the TARDIS. The pressure of the ship's air evacuating into space forced Alistair and the two guards to hold on nearby pipes. Its possible that Alistair survived but was killed when the Byzantium crashed into The Mase Of The Dead, the crash was caused by the Weeping Angel who was "dormant" all this time just to rescue its fellow Angels.