Kit Fournier is officially a diplomat with the American embassy in London but in truth he is the CIA bureau chief there. He is also a man looking for love and when he finds it, he finds himself in a great deal of trouble in 1950 and forced to become a double agent for MI6.
[Note: this is billed as the first book in the Catesby series. According to what I read, he plays a very small role in the British version of the book though the American Kindle version has no mention of him.]