Visible crew/equipment: When Number 2 and Number 6 are talking at the beach there is a shot of Nadia getting into the sea. Just before she takes her sunglasses off you can see rows of spotlights reflected in them. This is because the scene was shot in a studio and not a real beach. (00:15:25)
Visible crew/equipment: When the unconscious body of Nadia is being dragged onto the beach by Rover you can see the distinct shadows of two crew members and the camera being cast on the ground. (00:18:06)
Visible crew/equipment: When Number 6 meets Number 2 at the hospital, the shadow of the boom microphone is visible moving around at the top of the screen (on the wall), just before Number 2 greets him. (00:18:53)
Answer: It's even more obvious than you think, you know who number 1 is in the very first episode. When 2 replies to the question "who is #1?" Change the way he answers from you are number one (in the monotone or accented answer to, "You are, number 6. The comma gives you the answer. #6 is #1. It's the tone of the answer.