With a lot of focus on Bond, Q, M, Moneypenny and Felix Leiter, the character of Tanner (MI6 Chief of Staff) is often forgotten. However now five actors have played the character, and he also has a role in the books. Any favorites among the "Four Tanners"? The first one was Michael Goodliffe, who appeared briefly in The Man With The Golden Gun. The second Tanner, James Villiers, stands in for the recently deceased Bernard Lee's M in "For Your Eyes Only". In "Goldeneye" and "The World Is Not Enough" Tanner is played by Michael Kitchen. Like Bond, he appears skeptical of the New M played by Judi Dench. Finally, a new Tanner, Rory Kinnear appears alongside Judi Dench's "New" M. Oops, messed up the poll....sorry...
I liked Goodliffe. He sort of had an English nobility thing going for him which is how I always pictured Tanner as in my mind's eye. It's interesting because at first I thought the guy in CR was supposed to be Tanner--I forget his name (Villers, or something.), because ht actor sort of looked like Goodliffe.
Not the first one I'd seen, but for me it's Michael Kitchen (Mind, I also enjoyed his work in Foyle so...)
Tanner's supposed to be an ex-sapper who had a mine explode in his face, so I'm thinking Daniel Craig would be the ideal Tanner for Owen's Bond. So far, none of the film Tanners are anything but exposition, so I consider them equally irrelevant.
According to the Wikipedia article, he's in M's office at the beginning of the film, when they show Bond the letter and the gold bullet with "007" engraved on it. He's never identified by name in the scene. Come to think of it, I don't think he's identified by name in For Your Eyes Only either; Frederick Gray (the Minister of Defence) and Tanner are in M's office (standing in for the deceased Bernard Lee), but Bond only greets them as "Minister... Chief of Staff." It's not until GoldenEye that we see Bond and Tanner as friends (though I can't remember if that was established in Fleming, or not until the Gardner novels when Tanner became a regular supporting character). In response to the OP, my favorite Tanner would have to be Michael Kitchen, since he's the only one so far to even have a semblance of a character.
If I recall right, in Fleming's books Tanner tends to be the chap who's worried how Bond's coping following some recent trauma, but urges M to give him a chance to 'get back on the horse' with one more mission when M's doubtful.
Fleming's books very clearly have Tanner as Bond's best friend, but they don't really do anything together in the books until Kingsley Amis wrote COL SUN.