I didn't see it but it sounds a bit like something he did before involving members of the public being advised to back a certain horse - their horse always won.
He explained it all of course but don't ask me to explain it now.
That was The System, he started with 1296 members of the general public and they were texted to watch a certain race, with a certain horse to win - he covered every combination of possibilities.
The 216 winners were then texted to bet on a certain horse in a certain race, again covering every combination of possibilities.
The 36 winners were then phoned by Derren and told a certain horse in a certain race and to put on a bigger bet.
The 6 winners were (at this stage totally sucked into it) then met individually by Derren and given a certain horse in a certain race to win.
The winner was met at a racecourse by Derren and encouraged to bet a huge sum (4 grand I think) - the horse lost but Derren told her he'd actually bet on a different horse (accidently) and it happened to be the winner, he gave her the winnings - in fact he had bet on all 6 himself.
Or something like that - it may have started 1 level higher with 7776 people - I cant quite remember, but it was very cool.
The first 40 minutes or so of the program just followed the 1 girl who won in the last race, at some point the contestants were sent out camcorders to record themselves - so to the viewer (who wasnt seeing any of the losses) just watched this one girl win, then win, then win etc...
He showed how it was done using a different example where he showed himself flipping a coin and getting heads 10 times in a row, with a clock on the wall behind to prove it was an uninterrupted stream. What he didnt show was he had spent 8 hours (or so) flipping that coin knowing that the odds would eventually come up in his favour of 10 flips heads up. So there were hours of footage - but only the few seconds of all heads up were shown.