How Derren Brown "Predicted" The Lottery Results - My Guess (Updated)

Well, for the record this is how I think Derren Brown "predicted" the lottery results last night...

Identical sets and a body double?

I think there were 3 identical studio sets. The first section of the show was filmed on set one with Derren and was live. The middle point (where Derren moves to the right of the screen) was a quick cut (very smartly done) to a body double on set 2 watching the results. This gives the real Derren enough time to record the end section of the show on set 3. This end section is then cut to (again very cleverly). I think this last cut happens some time around when the TV is turned off but I'm not sure.

In fact I'm not sure about any of this but it's my best guess.

UPDATE: After thinking on this some more I realise that it's probably feasible to do this with just 2 identical sets as at the first switch the first set could be re-used. Also wondering whether this method could be achieved with mirrors and multiple sets instead of a camera cut.