In March 1942, over 600 men volunteered to steer an obsolete First World War destroyer packed with four and a half tons of explosives into one of the most heavily defended ports in occupied France. This episode examines Operation Chariot, the St. Nazaire Raid, and the strategic logic behind it: the German battleship Tirpitz could only be repaired in the Normandie dock at St. Nazaire, the single dry dock on the Atlantic coast large enough to hold it. Destroy the dock and the Germans would never risk sending the Tirpitz into the Atlantic. We explore why bombing, secret agents and naval bombardment were all ruled out, and how Combined Operations settled on a lightened ramming destroyer that could slide over the mudbanks in the dark.

We follow the ten-day conversion of HMS Campbeltown, including funnels cut to mimic a German torpedo boat and explosives encased in concrete, then the night itself: a failed RAF diversion that put the garrison on alert, a stolen German signal code that bought six precious minutes, the ramming at 1:34 a.m. only three minutes behind schedule, and the slaughter of the wooden motor launches meant to bring the commandos home. We cover Lieutenant Colonel Newman’s three orders to his trapped men, the five who walked to Spain, and the delayed acid-pencil detonation that went off at noon while Commander Beattie was being mocked by his interrogator.

• Why the Normandie dock was the linchpin of Germany’s Atlantic naval strategy
• How the acid pencil detonator worked and why cold weather delayed the blast
• The demolition teams who ran into firefights armed only with sidearms
• The cost: 169 killed and 215 captured out of 612, and five Victoria Crosses among 89 decorations
• How Hitler’s fury led to a massive expansion of the Atlantic Wall and the Tirpitz never left Norwegian waters