Sean Richardson is an agent with British Intelligence.
'Disgraced agent' is the way that the blurbs for each of the adventures describe him and that is pretty much the truth although it is interesting that while his name is not spoken with any welcome or affection in the upper levels of the management, they sure seem to call on him to take on near impossible missions.
We first meet him in a situation in 2001 when he is an agent in very good standing operating in the Middle East and Afghanistan. He "had travelled the world extensively in his role as a British intelligence officer. He was athletic, slightly tanned, adorned with slightly greying wavy brown hair, now in its long mode in a ponytail, and had the rugged features of an outdoor man. He was a tough, no-nonsense operator with a blend of charm and guile to suit his quiet but determined persona. Highly skilled, adept, harnessing a fierce loyalty and with talented spy tradecraft, he was quick-witted and comfortable amongst different people, cultures, languages and customs, and with the hidden perils his service brought."
In the same adventure, when the time setting jumps up to the present (2016), we have a totally different Richardson, the disgraced one mentioned at the beginning. He is "incarcerated in Kabul's most fearsome prison", now a "bald, gaunt" man who is "hurting emotionally, wounded physically, dejected at his demise, mentally on a knife edge". After having messed up a mission very badly, Richardson would find himself thrown into that prison for "having a huge stash of heroin blocks and illegal weapons in his hotel room". Fifteen years was the sentence and he would still be there now if his talents were not needed by his former employers.
Once he is somewhat 'rehabilitated' Richardson will find his services in need more than once but even though he will again prove he can deliver, he will always be on the outside.