Originally posted by Uries
As a matter of fact I read somewhere that these 'grand masters' were just actors
Not true. Well, you might well have read it somewhere, but nevertheless the players involved - all bar one - are well know in England. One of them, Chris Ward (GM) did a lecture at my club a few years ago and talked about the experience of filming with Derren Brown.
I think I agree that the players involved probably did have an inkling as to what was going on.
For chess players the 'trick' might be rather old hat and well known. Amongst non-chess players, however, it went down very well. UK residents are blocked from these Channel 4 Derren Brown clips now but they didn't used to be. For some time when this was accessible from Britain it was amongst the most viewed of all Derren Brown clips on youtube.