It was incredibly obvious from Alastair's reaction that he was in desperate need of something, though if it was because his needs had been neglected (probable, given the Weasley kid's injuries) or if he was always like this (less probable, but still hot) he didn't know and he really didn't care because the reason behind the hunger didn't matter in the moment. All that did matter was that they fed the hunger, because Rook had been waiting for this moment for a long time--considering how little time he actually spent on securing the men he slept with, anyway.
His mouth didn't stay on Alastair's for very long, just like his hands didn't stay on his sides for very long either. One hand traveled down the long line of the other man's body until his fingers wrapped around the back of the knee at his hip, while the other slipped behind Alastair's lower back, palm flat against his backside, far too low to be decent, to use as leverage to keep their lower bodies together as he moved against him; meanwhile, lips and teeth skated over exposed skin on his neck. That is, until the first warning bite was given, to gauge Alastair's interest by his response to it. Rook hoped he wouldn't be disappointed, but if he wasn't into it, he wasn't into it.