Alex Jennings as Barnes Wallis?
Recently saw a documentary on this, the one presented by Martin Shaw who seemed to be dolled up to look like Barnes Wallis - well, they could do worse I suppose.
I don't know if Sir David Frost's movie will ever see the light of day, but if so they should perhaps consider Alex Jennings as Barnes Wallis - they really do look very similar. It's uncanny. Jennings was in The Wings of a Dove with Helena Bonham Carter. He's also a stage actor, he was in the West End's My Fair Lady.
As for Guy Gibson, he was not as sympathetic in real life as Richard Todd, hardly one of the lads. Hard to cast, to find a 23 year old who could pull it off. I would cast a member of a boy band! Yep, you read that correct. He might be able to pull it off, and I think the film should expose some ambivalence about the people involved, what they're trying to achieve and the morality involved. Not, perhaps, unlike The Social Network, about the founding of Facebook. This needn't be a propoganda piece any more.