Examiner talking during the nav?
Hold up your hand and say "Please, I'm concentrating".
Any more "chat" (at the wrong time) moves towards a Regulation 6 appeal.
I've always been a great pro-ponent of 'chatting' to candidates on test - but only to PPLs. Partly to calm their nerves and partly to see how they would handle the situation when 'passenger' starts asking daft questions at wrong time.
CPL? Not allowed to open chat to candidate (altough CAN respond to his/her chat) - certainly during nav - I emphasise it on the pre flight brief. "I'm going to go very quiet, just to give you 100% opportunity to concentrate. Please don't think I'm being unfriendly"