So, in one of my ideas for a novel I'm juggling with, there's a top secret government organisation. It's not like MI5 or anything like that, it's something the public don't know about, and shouldn't, as it deals with a very scary threat. Think Department 19 in Will Hill's book of the same name, and you get the idea. The people in this organisations, the high ranking ones at least, are referred to as "Agent", though I don't always use this term when referring to them in narration. My issue is how to name the people that work for this organisation, bearing in mind the fact they'll be interacting with other people outside of it. Since the organisation is all hush-hush, and security is paramount, I'd originally thought to use codenames, for example "Agent Lance". However, although I'm happy with the individual codenames I've come up with, I still think the idea is perhaps a little silly, or just not right. I thought that using surnames may be a better idea. So what do you all think? Codenames or Surnames?