In the summer of 1944, Londoners learned to fear silence. The rhythmic buzz of the German V-1 flying bomb, the Fieseler Fi 103 known as Vengeance Weapon 1, meant a pilotless machine was overhead, but when the engine cut out, 850 kilograms of Amatol explosive was already falling. This episode uses declassified MI5 reports, German engineering schematics, and wartime diaries to unpack the birth of the world’s first cruise missile, a weapon that could strike a city hundreds of miles away without risking a single pilot.

We break down the surprisingly crude technology that made it work: the Argus pulse jet firing 42 to 50 times a second, an analog autopilot driven by compressed-air gyroscopes, a magnetic compass housed in a wooden sphere, and a nose propeller wired to a mechanical odometer that triggered the terminal dive. Then we follow the desperate Allied response, from anti-aircraft guns bolted to railway sleepers and radar-fused shells to fighter pilots wing-tipping bombs out of the sky, and the MI5 Double Cross deception that quietly shifted the German aim away from central London.

• How the Walter catapult used hydrogen peroxide steam to fling a V-1 past its 200 mph stall speed
• Heinkel 111 air launches over the North Sea and the piloted Reichenberg variant tested by Hanna Reitsch
• Operation Diver: proximity fuses, fire-control radar, and 2,000 barrage balloons defending London
• Why double agents Garbo and Tate reported real bomb strikes that fell short of the city center
• The V-1’s legacy as a cheap, expendable drone copied by the Americans, Soviets, and French