Caroli admitted that he was a spy but initially refused to break his oath even when threatened with death. His friendship with Schmidt gave his interrogator a different point of pressure. A promise to spare his friend's life persuaded him to reveal Schmidt's identity, equipment and approximate landing place, along with their private plan to meet in Northampton. Giving information still did not mean he would immediately work as a double agent. He accepted that role only after further persuasion that the Germans had sent him to Britain poorly equipped and under false pretences. Under the code name Summer, he became another means for MI5 to communicate with German intelligence.
Notable Point · 1:37:36-1:39:42
How Caroli's friendship with Schmidt broke his resistance
Concern for a fellow agent overcame Caroli's willingness to die for his oath, but recruiting him as a double agent required another step.