Possibly you all are already aware of this one but, if not, the Chevalier d’Éon was quite a person.
I saw a talk a few years ago by a gent called Victor Gregg. He’d served in the British Army - literally press ganged by a recruiter (“hot meal for you son, just sign here…”).
Escapdes included travelling alone across the north Africa deserts, routinely secretly meeting with Germans at night to swap cigarettes for booze (and then doing his damnedest to kill them the next day). At one point, he was captured by the Germans, and held in Dresden… just before the city was firebombed. He escaped from a blazing prison.
After the war he joined MI6, and became a communist. Not a double agent, mind you - a patriot who faithfully served his country, but who happened to believe in communism.
The talk we saw - at a literary festival - was by Mr Gregg himself, and the writer who had ghost-written his book. Amazingly, the ghost managed to turn that lot into a dull read.