David Nairn is a high ranking leader in the British Secret Service.
Nairn is an old horse in the Intelligence field, having been around for nearly thirty years and having worked in numerous areas of the world. Though some of his missions earlier in his career are told in flashback, most of the activity in the five-book series revolves around his role as Deputy Director of Operations, responsible for handling other agents and generally running the show.
Nairn lives a mainly solitary life in a dingy apartment. He was happily married for many years but his wife died a decade before in a car crash and he has acquired a habit of not taking the kind of care she was once so determined to do. By his own description he has "gaunt, weather-beaten skin stretched tight over angular bones" making him appear ten years older than he was and he was easily in his early fifties.
His frequent travels and changes of assignment precluded his amassing many possessions and greatly stunted his social life. Complicating matters, he suffers from a very bad heart and has to take time off at one point for serious heart surgery.
Through all that, he remains an intrepid warrior against the communist forces trying to take over the world even as it struggles to remain in existence.
As the series progresses, Nairn begins to make more and more use of a female agent that he learns to greatly respect. As an agent, Sarah Coble is not afraid to take chances or to put her life in danger to get the job done. Nairn sees a lot of himself as a young agent in this woman.