Tavy Martin is a part-time agent for British Intelligence.
She has had no training as such and she is used only twice but both of those times she has been asked to place herself in harms way to root out perpetrators who seek to bring trouble to Her Majesty's government.
Her first name is really Octavia, which she never uses, preferring 'Tavy'. Her normal line of work is in the Public Relations department of the Ministry of Defence where she is a secretary. She is fairly young, quite attractive, and very smart. She has no serious relationships, choosing instead to have a fair number of men whom she dates, although there is a Naval officer named John that she is starting to think twice about.
Her experience with clandestine work comes about because of Charles, an older man with a fairly high position at the MOD and connected to British Intelligence, a man she has known for some time and with whom she once had a brief affair even though he was married. Still friends and still affectionate, though not intimate, she is willing to listen when Charles approaches her to take on the first assignment.
For his part, Charles did not intend that Martin should get deep enough to be endangered. He needed someone to ask questions at the Portsmouth Naval Yard and he knew any agent he sent in would be suspected as an outsider. A young woman who transfers to that area to be with her new boyfriend, however, would be accepted readily, especially when that woman was as friendly and personable as Charles knew Martin to be.
So it is that Martin is sent to handle her first unofficial case, a matter that takes a more dangerous turn than either of them expected. And some time later when Charles again needs someone unsuspected, he knew who he should call.