Charlie Muffin is an agent with the British Secret Service.
If Lt. Columbo had been a spy, he would have been Charlie Muffin. Or vice versa. Charlie is a public school product of the middle class who just happens to be better at the spy game than all the privately schooled superiors he is forced to work under. Two elements stand out about the character of this amazing agent. The first is that he is very good at what he does and the second is that he doesn't look or act like he is.
Muffin's clothes are always wrinkled, even when he puts them on newly pressed. He constantly wears hush puppies, regardless of the occasion, because his feet always hurt and they provide the least amount of pain. He is insolent in speech and rather quick to take umbrage at comments. He loves to drink and often suffers the ravages of too much imbibing.
Still, he is without a doubt the best man that the British Secret Service has ever had. He is the best at uncovering the truth. He is the best at shadowing or keeping from being shadowed. Most importantly, he is the best at survival, a goal he keeps at the top of his priority list at all times.
Being good and being seen to be good can be totally different things and Muffin finds this out rather emphatically. When the old hands who ran the Department finally retire or are pushed out and replaced with young blood, relics like Muffin who do not look the part, do not act the part, and certainly are not from the right background are discounted and vehemently disliked. When an occasion arises that needs a fall guy, someone expendable, Muffin is the choice.
It is at that time that the true genius of Charlie Muffin is revealed. Muffin may not look like much and he acts like even less but he is the best survivor the Service has ever seen and the young punks in charge will come to learn that fact and regret having ever chosen him to take the fall.
As the series progresses, Muffin is some times on the outs with the Service, some times actually hunted by them, but eventually an understanding comes to pass. They learn they cannot beat him and he learns that he needs the work, and the challenge.
Muffin's life takes many a strange twist in the books which span two decades and see him aging alongside them. One thing that never changes, though, is that Charlie Muffin is one of the best that there has ever been.