All the answers seem to point to camera trickery but for me it's a very, very cheap way to do this.
I can't see Derren resorting to use of a camera trick (even if it's seemingly obvious he has) - purely for the fact that it's not magic and if it is illusion, it's been too easily explained by anyone with half a clue.
If it is camera trickery, I can't help but feel this event will be tied into the next one, which is something like 'how to control the nation'.
He stands to lose a lot of respect and followers if it's something as poor as a split screen.
I can't see Derren resorting to use of a camera trick (even if it's seemingly obvious he has) - purely for the fact that it's not magic and if it is illusion, it's been too easily explained by anyone with half a clue.
If it is camera trickery, I can't help but feel this event will be tied into the next one, which is something like 'how to control the nation'.
He stands to lose a lot of respect and followers if it's something as poor as a split screen.



