When I started Lord Alexander's Cipher; or, the Bridekirk Behemoth, I described it in the trendy "high concept" way as "Georgette Heyer meets James Bond."
The Georgette Heyer bit is fairly obvious - I was writing about the same social stratum, during the same historical period, and I wanted to achieve the same lightness of touch and subtle wit that she does so well. The finished draft now going through the NWS can reasonably be judged against that aim.
The James Bond-ness has evolved a bit. My hero was originally going to be the dashing secret agent type, with gadgets and cool one-liners, but he has turned out somewhat differently. I think that is a good thing, for at least two reasons.
Firstly I don't like James Bond as a character much - indeed I would argue that he is hardly a character at all, more a collection of attributes (poor taste in Martinis, good taste in cars) but with none of the flaws that might make him believeable, and thus make him work as a romantic hero rather than just an action hero.
Secondly, I didn't end up writing a Regency Q scene for him. I nearly did, and I have a bit of one left in the draft that doesn't go anywhere with a particular gadget, but I am glad that I didn't because I am currently reading Julian Rathbone's A Very English Agent and he does have a Regency Q scene. Much more knowing and arch than I would have tried, and very good. I would hate to have unknowingly produced a pale imitation of it in my story.