Germany built the Enigma machine believing its ciphers were unbreakable, and this History Hit episode follows the codebreakers at Bletchley Park who proved otherwise. Alan Turing anchors the story, but the film widens out to the wider team and machinery involved, tracing the leap from early manual cryptanalysis to the electromechanical bombe and then to Colossus, the valve-based computer built to crack the more complex Lorenz cipher. Archival photographs, wartime footage, and location material from Bletchley Park itself sit alongside expert interviews explaining how the resulting intelligence, codenamed Ultra, reached Allied commanders without tipping off the Germans that their codes were compromised. The film lays out concrete cases where Ultra intelligence shaped Allied decisions, from convoy routing in the Battle of the Atlantic to planning around D-Day, and addresses the long secrecy that kept the operation hidden for decades after the war. It is a straightforward, well-sourced account of how a code-breaking operation became one of the war's decisive but invisible weapons.