Some time ago a man in a wheelchair was on the programme and they had an access ramp ready for him.
Today's contestant, an air hostess, said that her husband attended previous shows with her, but when he knew that she was going to be on today, he left because he did not want to appear on TV.
It is now obvious to me that the contestant is chosen the day before the show is screened. This seems to be a good idea as it lets the player have time to think of what they are going to say on the show
Yes the contestants know when they are to be 'chosen'. And there is quite a lot of rehearsed chat too especially between Edmonds and the 'Banker'. Also the cameras always seem to catch the unexpected reaction or expression - that's probably why it's not unexpected.