There's an interview here where he talks about having used photoreading itself (in here it is typed "photo-reading", with a hyphen, for you apple-Find folks) but also various other techniques that tilted the scales in his favor. He does not, as far as I can see, say it's a sham -- only that people seeing him do that should not expect to do exactly the same thing just because they take a photoreading course.
Jamy Ian Swiss / For fans & magicians / Derren Brown Conversation
Thought y'all might find this handy. ^_^
Megan M.