These shows involve illusion, manipulation, deception and a big "reveal" at the end. Certain aspects of what the contributors will experience cannot be discussed during the screening process. I therefore have to use other methods and sources in addition to the interview (eg psychological tests, family interviews, medical records) to make sure that the contributors can cope with the whole process of filming and transmission and that producers can cope with the contributors!
I have worked on several Derren Brown programmes including The Heist (2006), Trick or Treat (2007/8), Hero at 30,000 feet (2010) and Miracles for Sale (2010). Contributors are usually fans of Derren's and know to expect the unexpected. Derren does his own screening for suggestibility.
This was an unusual project, filmed on a disused military airfield in Suffolk. Candidates were recruited by producers as "adventurous thrill seekers". They believed they were training in Russia for places on the first British space tourism flight. A huge simulator was constructed, with panoramic video screens of space. Russian speaking actors were hired as crew.