Alistair (The Time of Angels)

 was an acquaintance of Doctor River Song, with whom he had danced. He realised River was onboard his ship, the Byzantium, when he discovered one of his guards with Hallucinogenic lipstick on his face. When he encountered River, Alistair intended to have his guards kill her 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 Eleventh 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. It is unknown what happened to him when the Byzantium crashed into the Maze of the Dead. The crash was engineered by the "dormant" Weeping Angel. (DW: The Time of Angels)