Mike Brady is an agent with SM-7.
That designation represents a small but effective department in the British intelligence community, led by "a grey haired, distinguished man known as Sir Charles". It is likely connected to that nation's Defense Ministry. It has its headquarters "at the top of an unimpressive building in London's West End".
In the first recorded adventure we learn that to most people, Brady is a freelance reporter but in truth he is "something quite different - a tough secret agent". That difference extends to having an assistant, named Mandy though he calls her 'Beautiful'.
Brady appears to be in his mid 30's, with some shots making him look a good deal younger and some older. He wears moderately short (considering the period) dark hair and is considered quite handsome with his solid good looks and extremely confident demeanor.
It is not known if either SM-7 pays extremely well or Brady is independently wealthy but considering the clothes he wears and, more to the point, the very snazzy sportscar he drives, he has to have a lot of disposable income.
Mandy is an important member of the team. In a more modern setting she would undoubtedly be considered a junior partner. She maintains things in the office as would be expected of an assistant but she is much more than just that as she is up on everything her boss is doing as well as the bad guys he is likely to encounter, not to mention also racing to his aid when she rightly deduces he is in danger. In truth, in both the adventures we have of Brady and Mandy, she has to save him and even lightly admonishes, "you always get yourself in tight spots and I have to get you out. One of these days I won't be around..."
A couple things that help is the fact that she has a photographic memory and can pull up facts quickly, she is very skilled at judo and not the least bit hesitant to use it, and her throwing arm and quick reactions are quite impressive.
Her looks change over the two adventures with her having long blonde hair in the initial one and long black hair in the second. The two also have a personal relationship outside of work.
Together these two make a pretty impressive and enjoyable pair of operatives.