The crash drew Greg's attention too, though he could at least see what was happening without having to turn away from Ron. He'd forgotten how noisy wizard chess could be, and he'd never played it with pieces on this scale. With a shake of his head he returned his attention to Ron. "Go on then," he suggested, pleased he wouldn't have to back down. "I'm leaving anyway." He didn't want to stay here, with the noise and the people who thought they were better than him. Besides, he still had that nagging feeling that he was supposed to be somewhere. Since it obviously wasn't here, he was probably late. People were mostly used to that from Greg, but if he didn't turn up at all he knew they would come looking for him.
"Enjoy your stupid chess," he added as he half-turned to head down the stairs. He only hesitated because it was Weasley, who was still classed as 'enemy' in Greg's mind and he didn't want to turn his back on him without a shield in place.