This probably isn't that much of a surprise, unless you genuinely believed that Derren Brown genuinely had some magical mind-control abilities or something. All of his productions rely on some sort of psychological manipulation or suggestion, tricking people into doing things they wouldn't normally do. These techniques aren't the complete invention of Brown, but rather come inherited from a number of traditions, including cold reading and other sorts of manipulation and misdirection that have been used by stage performers for decades. What you might not know is quite how much of a geek he is for proper, scientific psychology, and how often he relies on it for his shows. In 2006's The Heist, for example (where he recruited a bunch of people off the street and convinced them to rob a white van on a high street in broad daylight), he shamelessly reconstructed the famous Stanley Milgram obedience study from the sixties, seeing if people would willingly administer electric shocks to an individual if instructed by an authority figure. Brown took it a bit further, suggesting that the victim was suffering a lethal dose of electricity - obviously they were an actor, and a pretty good one too - but that's not the first time he's relied on the history of psychological study to pull off some of his stunts. The Gameshow episode of The Experiments co-opted Zimbardo's experiments into deindividuation to make crowds act in morally questionable ways, and both Messiah and The System took advantage of confirmation bias, where people tend to believe what they want to. What a nerd.
Tom Baker is the Comics Editor at WhatCulture! He's heard all the Doctor Who jokes, but not many about Randall and Hopkirk. He also blogs at http://communibearsilostate.wordpress.com/
