From A Woman of No Importance: The Untold Story of the American Spy Who Helped Win World War II, by Sonia Purnell (Penguin, 2019), Kindle pp. 138-139:
SOE had decided it was time to hit the Free Zone, while it still existed: to move on from the niggling small-scale attacks they had so far organized to detonate carefully selected “big bangs.” Virginia was soon ordered to dispatch Cowburn to sabotage the entire railway network around Lothiers in central France, using the specially equipped groups of men they had spent months training. She also took delivery of two hundred thousand francs to arm and instruct teams for, when the time came, taking control of Lyon’s Perrache station and a nearby airfield, as well as blowing up a power station.
Parachute drops of arms and explosives were generally being stepped up, when clear skies and light winds permitted. New agents came in with dozens of false-bottomed suitcases with warm clothing for the forthcoming winter on top, hiding explosives below. SOE “boffins” (or scientific blue-sky inventors) based at the Thatched Barn, a former hotel on the Barnet bypass in north London, had secretly designed a range of ingenious explosive devices to cause maximum impact in the most challenging situations. These real-life forerunners of James Bond’s Q had come up with milk bottles that exploded if the cap was removed, loaves of bread that would “cause devastation” when cut in half, and fountain pens that squirted poison. Perhaps the most popular was fake horse dung that exploded if driven over—but there were also tiny but lethal charges that could be inserted into cigarettes, matchboxes, bicycle pumps, fountain pens, or hair brushes, and perhaps most usefully railway engines or fuel tanks. On a larger scale, for the first time there was even talk of moving on from sabotaging industrial sites to identifying “A-class” or military targets to hinder the German counterattack in a future Allied invasion. Virginia’s months of slog and preparation appeared to be leading to real action. Finally, it seemed as if SOE had the critical mass and the direction needed to do something truly significant, and she wanted more than anything to see it through.