Matthew McFadyan - I think he's completely gorgeous, apart from his Darcy wig... He's a bit solid-looking for Dr Who, if you follow DT's fey (in a good way) sort-of fragility. Stephen Mackintosh better for that style, perhaps, and very cute.
Can't be John Simm because he played the Master - or I would definitely have said yes to that. I think Matthew McFadyan - if he's the one in Little Dorrit - has too litle menace about him. The Doctor always needs to appear as scarey as the baddies, something Chris Ecclestone and David Morrisey can do - comes from them being a Mancunian and a Scouser respectively, perhaps. What about James McAvoy? Casey???
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Not Casey for Dr Who, obviously, just, Casey, whaddya reckon - knowing you've got the hots for him?