Cass was actually having such a good time that he'd nearly forgotten that he'd promised Lettie to talk to Terry. Actually, since he spotted Terry kissing the MacMillian he'd lost interest and forgotten he was even there - until he saw him speaking to Percy.
He wasn't sure he noticed, but he did, and once he'd noticed he remembered he needed to talk to him. Percy surely had nothing to do with him moving closer. Not this time. And he actually did wait until they were finished before he moved in.
'Hey there,' he said with a smile. 'You've done a great job,' he said, the teasing and flirting from previous meetings gone from his behaviour.