 The RN 's Operational Intelligence Centre selected the route and timing for the raid based on intelligence about the location of minefields and German recognition signals sourced from Enigma decrypts and knowledge of Luftwaffe patrols compiled by the Air Ministry 's Air Intelligence Branch . When all the plans had been pulled together and the timing worked out , the raid was expected to last no longer than two hours . The commandos and crew from Campbeltown would board the motor launches at the Old Mole jetty and then return to base . 
