no wonder watso was never interested in any "magic" shows that used to be on tv. one can assume that with camera's time delay, special effects, - then anything can be done.
the explanation in the clip provided by canyoubus seems to be supported by similar clips.. simply a split screen.
watso had a look at a few clips involving derren brown, and he actually explains how he did the trick. a real good one was the following
http://www.youtube.com/watch?v=evZmpsl3jI0
in this he simultaneously played chess against 9 super chess players . he explained that all he really did, was to pair the players against each other (4 pairs of 2), and simply (well, it is not all that easy to "simply" ) remember the moves. when he got around to the other "pair"
