Confessions of a Conjuror - Derren Brown

"This tutting, eye-rolling signal is related to the gesture we might make on the street after realising that we are walking in the wrong direction from that where we wish to head. Wanting to turn round but fearing the attention we will attract by breaking rank and turning one-hundred-and-eighty degrees for no clear reason, we decide to use a cartoon-gesture that denotes ‘Having Forgotten Something’: we raise a forefinger slightly to make a minimal ‘A-ha!’ point, raise our eyebrows, stop in our tracks and provide a visible motivation for the very public rotation we are about to perform. ‘Look,’ we imagine people will think, ‘that guy has realised he has forgotten something; how sensible that he should now turn round and attend to it. What sound judgement on his part.’ If we were alone, we would not make that cartoon-gesture of sudden remembrance."