The Times Online has an interview with Toby Spence on his part as Candide. He mentions Alex and the difference between actors and opera singers:
"Spence obviously can't wait. He thrives on Carsen's brand of aggressive theatricality, and is keen to work with stage actors (Alex Jennings plays Pangloss). “Every day I see him adding something, or taking something out. Whereas we opera singers arrive having made a lot of decisions, he's putty, and that's fascinating for me.”"
For the full interview see: Times Online