A good, even-handed documentary series.
This episode focuses on the SOE -- the Special Operations Executive -- created by Churchill to infiltrate and confound Britain's enemies in World War II.
The first impulse behind the creation of the SOE was to "set Europe ablaze," meaning destroy everything that aided the German occupation, such as blowing up factories along with the workers inside. The was, fortunately, rethought.
The Support Department was responsible for producing the necessary tools, such as miniature pistols, fake documents, and (really) exploding cigarettes and itching powder to be used in German underwear.
In "The Guns of Navarone", explosive expert David Nivens tries to sabotage a battery of huge guns by slipping an exploding rat into the works. The rat wasn't made up for the purposes of the movie. It was real, and developed by the Support Department of the SOE.
Of course they went far beyond weapons. Spies in Europe wore clothing taken from refugees, and sometimes cut to a tight Continental pattern rather than the looser British style. What amazing precision, but then a great deal depended on its simulated authenticity.
France was relatively easy. But the farther away from England the network operated, the more difficult and less efficient it was. Poland was a trial. And the Circuit Chief in Egypt was asleep at the switch, which was even more damaging because the Balkans -- Yugoslavia and Greece -- were ridden with local political rivalries.
It was dangerous work. If the spies were found out they were executed or sent to concentration camps. One quarter of those sent to France didn't survive. I wouldn't have made a good SOE agent.
A full-length feature (clips of which are used in this documentary) made after the war used reenactors to show how the spy business worked in France. The title is "Now It Can Be Told" and you can find it on YouTube, I think.