David Suchet already discounted - ditto Hugh Fraser, Philip Jackson, David Yelland & Albert Finney.
Jason Isaacs - No, too young looking, hair too dark
Alfred Molina - No, too young, hair too dark, nose wrong, chin wrong
Ian Holm - pretty sure already mentioned. Not him. Hairline too high, face wrong shape.
Rupert Everett - No. Not someone this well-known. Hairline maybe a bit too high. A bit too young. Ditto Martin Freeman.
Toby Jones- No. Too short. Hair wrong. Just not him (despite him being in everything, ever!)
Alex Macqueen - No. Too young. Too bald, eyes wrong
Bill Nighy - No. Nothing at all like the person I'm trying to think of - and not someone as well-known. Could possibly be the right sort of age though. But always worth checking out pics of Bill :)