The Invitee

He didn't quite get it. Merlin didn't quite understand why Arthur would invite him for a drink with him and his friends, the knights. It's not that he was complaining, but he hadn't done it before so why now?

Arthur on the other hand, knew exactly what he was doing bringing Merlin to a pub. As far as Arthur knew, Merlin went to the pub regularly and couldn't pass up a good drink. With Merlin drunk he could figure out what his servant was hiding from him all this time.