Alistair (The Time of Angels)

 was an acquaintance and possible former lover of Doctor River Song for whom he had danced with in the past (DW: The Time of Angels). He came to the conclusion that River was onboard his ship when he discovered one of his guards with haluconagenic lipstick on his cheek. When he ecountered River, Alistair had intended to have his guards kill River and make it look like she was trying to escape, but she had delayed him long enough for the door to open into space and her to be rescued. So, when River escaped from the Byzantium to land in the TARDIS, the air pressure forced Alistair to hold onto a nearby pipe so that he did not fall out into space. The Byzantium later crashed, killing everybody on board, except for the lone Weeping Angel, which was held in the bottom of the ship.