Michael Vaux is an agent with MI-6.
As the series begins he is not an operative and would frown at you should you mention the possibility. Vaux is a reporter with a very hefty resume and a lot of stories under his belt. He is also unemployed and thinking what he will do next. Vaux would never say that he went looking for work with the Secret Intelligence Service; it just came his way. He was, though, looking for a job because the newspaper at which he work for quite a few years had laid off a fair number of the older reporters. Seniority meant experience which invariably meant higher salaries which in turn lowered profits. Juniors could demand less so got less which Vaux understood with no bitterness but then no steady paycheck other than his small pension.
Most of his career in the news game was in America and he was comfortable there. He left Britain in his early thirties after several successful years on Fleet Street. In the States he worked for a couple of different, impressive titles include Time Magazine. Add to that the fact that before all that he attended Bristol University where he studied economics and law, both topics making his writing about such subject more understandable and less clinical.
When he was let go, though, he realized that Britain, though, was home and now that he no longer had a job to hold him, he decided a trip back to the land of the Union Jack was in order, which is why he was in the position he was when life around him would change his already changing life. He is actively looking to buy a house in his old neighborhood which is where the people from MI-6 will find him when they have a need for someone with his background and, most importantly, his cover.
History is replete with operatives taking the cloak of journalism to hide their real identity. To have a true journalist with all the credibility one could hope for actually work as a spy is a different story.
Vaux, by the way, as it is pronounced, rhymes with faux or, as he mentions in the first adventure, like "veau", the French word for veal (no, me neither).