Alistair (The Time of Angels)

 was a presumed acquaintance of Doctor River Song for whom he had danced with in the past. 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.

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.