MI5, while fairly inept early in the war, were rockstars later. Every single German agent in England was turned and used for misinformation. The Double Cross network helped in disinformation campaigns vital to winning the war. They also kept London from being obliterated by V1 and V2 rockets, agents falsely reporting hits in the city center which the Nazis believed over the telemetry readings! The rockets were retargeted off course by miles.
|Juan Pujol, aka Garbo
Pujol, first in Lisbon and later with his MI5 agent, created 27 false sub-agents, the Nazis paying him for all of them. These two men accomplished more than any other agent. Pujol was awarded both an Iron Cross and an MBE.
What I find hilarious is that, despite his intelligence and resourcefulness, in Portugal Pujol couldn't figure out the British pre-decimal currency system! He would submit expense reports untotalled, not knowing how. I remember reading Ballet Shoes when young and being utterly baffled by the currency. Only with the advent of the web and wikipedia was I able to find an explanation of the system.