A volunteer who participated in Derren Brown's "The System" special has posted a copy of the 25 January 2008 e-mail she received from Objective Productions (the company that produces Derren Brown's shows). The accompanying blog entry reveals details of the production:
1. participants were selected by responding to a newspaper advertisement (about 4 months ago);
2. respondents went through an audition process including on-camera interviews;
3. they were not informed that Derren Brown was involved; and
4. participants received an e-mail with a tip on a horserace, and instructions that they should not place a bet on the race.
All of this is consistent with a comment left on this blog by another participant in the show, and with my own prediction about the upcoming special (see The Secret of Derren Brown's "The System" -- A Friendly Wager).
The show airs this Friday (February 1, 2008) at 9 PM on Channel 4.