Michael Kells is an agent with the British Secret Service.
I have categorized his employment for the two recorded adventures we have of him as working under the direction of renowned spymaster Peter Quayle who, during the Second World War was in charge of a small cadre of highly dedicated and extremely deadly field agents. I put it this way because in the those two missions, he talks about his boss and even has meetings with him but Quayle's name never actually is mentioned. All references to his boss is using the (apparently to Kells) affectionate term "Old Man". In a different, non-Kells adventure, though, reference to his working alongside other agents who definitely worked for Quayle is enough to set in my mind Quayle being the Old Man. Certainly, Kells is part of the so-to-speak Quayle-verse.
When we first encounter Kells, he is suffering from what might be the unpleasant results of too much imbibing the night before. He tries to make sure we do not think badly of him for this, though. "You wouldn't get any funny ideas about me, would you? You wouldn't come to the conclusion that I was just another of those people who've become bored with the war and try to "sublimate" their annoyance by getting cockeyed all the time? I'm not a bit like that. But-and I think I should point this out now-when one has been in the sort of racket that I've been playing around in for the last few years, it's a very good thing for a man to relax occasionally-if you get me-just to stop himself going entirely nuts." Still, he does also let us know that the first thing he does upon waking and finding his trousers was to check his hip pocket to make sure the flask of whisky was present. It was and he soon made sure it had a bit less in it.
Kells is an interesting man in that he seems a bit interested in studying other people, gauging who they might be working for and how they might interact with him but he is definitely not the least bit interested in how those same people might view him. He can be a wee bit acerbic and while his tone is seldom insulting or argumentative, he can be short in conversation. This extends to his dealings with the Old Man.
In action, though, he is decisive and definite. He does not hesitate to ask questions or get physical if answers are not forthcoming.