Mirror, mirror

Three CRS push down the centre aisle - two white and one black. One of them stops and peers at the door to the loo, rasing his hands to his eyes as if he were gazing through the panelling. They move on to the end of the carriage, and lean against the glass. The two white ones engage in conversation, ignoring their comrade completely. After a while he moves in closer to them, changing position so that he is directly in front of them. The smaller white one shifts his shoulder round, blocking him out.