Jensen is a freelance agent with British Intelligence.
He does take contract work for the CIA as well but mostly, it seems, it is for the UK that Jensen does the majority of his work.
Did work, I should say. And then does again. The brief intermission was when he chose to take far safer - and more boring - work at home to be close to his wife, MJ, when they produced their adored Elena. He only returned to the previous contract work - and even then only on short-term contracts - when his wife noticed just how this mundane security consultancy work was to her husband.
We meet Jensen for the first time in a flashback scene as he is being roughly manhandled into a waiting vehicle by rebels who have thrown a black pillowcase over his head, hauling him off to some undisclosed location for a fate that did not look promising at all. He is not alone in this captivity as his long time workmate Marshall and one other were also taken. And this was not the first time that Jensen and Marshall had found themselves in such a situation so both of them had already prepared for the likelihood and had a plan. Their captivity was not long. The important aspect of the whole affair, though, was that Jensen and Marshall had wanted to get captured; it put them in proximity with a previous capture whose release was their original objective. Extremely dangerous but effective, a hallmark of Jensen's methods.
If you noticed that I did not give a first name to Jensen - assuming that is not his first name - it is because I could not see one for him in either of the two recorded adventures. Does his wife call him that as well? Probably not but that is all we have for this 6' tall man "with a muscular frame".
However, in addition to some very exciting and thrilling action, we are also given a lot - and I mean a whole lot - of very brief interludes detailing fascinating pieces of tradecraft. These all prove, to me, to be extremely interesting and though they come fairly frequently throughout the narratives, they enhance rather than detract from the proceedings.