Wish I could remember a few names. Might have to have a browse through the casting threads on the Lyst, but the trouble is that Paul Darrow made the role so much his own that I've never been able to see anyone else in the role - and that's transferred to Holland to some extent.
Colin Firth is in the "if we can't find anyone better" class, as far as I'm concerned. I wouldn't rule him out, but there must be better available. Ditto Pierce Brosnan. Rowan Atkinson has the personality but not the looks (I'm thinking Blackadder here, not Mr Bean
Here's a thought - Stephen Pacey matured into someone who might do very well in the role for anyone who isn't going to sit there thinking "Tarrant". He's fortyish now, and filled out into something less of a beanpole - and is not a bad actor. I haven't seen him in a substantial enough role to be able to judge whether he'd have the presence needed, though.