I think Brian is putting on this thick-guy persona. Reason being, because when he was singing Charlotte Church's "Pie Jesu" he sung "Pi-e" the first two times, and then changed it to "Pie"- as in the way it's spelt. Now this you would only do if you thought it was pronounced pie, because of the spelling. So why sing it correctly the first 2 times and then change it to make you sound like you are dim?
Hmm. Also not convinced about the Shakespeare thing either. He has said some very profound and grown-up things since. I reckon it's an act!