Dan Taylor is an agent with an unnamed arm of British Intelligence.
This unnamed, and possibly undocumented, group "advises the government about threats to national security" according to one of its managers, David Ludlow. Exactly how long the organization has been in existence is unknown but three years before the first recorded adventure, Ludlow and one of his men, a man named Mitch, were in the British army. That is how they knew Taylor and how eventually Taylor would be drawn into their circle.
Taylor was the son of a highly successful geologist and world traveler and experienced adventurer. It had been expected that his son, a man with every bit the brain power of the elder, would follow in his father's path through university and then the private sector. To the dismay of the father, Taylor had other plans. As he put it, he "just wanted an adventure he could call his own."
Which is why he enlisted in British Army. His intelligence and his desire for excitement is how he ended up in the extremely dangerous field of bomb disposal. And it was in service in Iraq during the conflict there that he learned the meaning of danger, and its results. Though he was alone in his blaming himself for the explosion that would end his military career and cost others their lives, the nightmares persisted.
The first adventure that Taylor would have with his old Army comrades takes place three years after the horrific events, three years of doing one contract job after another followed by a period of depression and drinking. He was going nowhere and had no hurry to not get there. Some might say he was desperate for something to give him purpose. He got it.