Was Churchill really the only person who could persuade Britain to keep fighting Germany?
Short answerNo, but he was probably the only leading Conservative political figure who could run the country at that moment.
NotesBritain's willingness to fight did not depend on Churchill alone. The narrower issue is practical party leadership in 1940. Among the major Conservative political figures, Churchill was probably the only viable choice to run the country at that point. Films can turn that contingent political position into a simpler story of one man creating national resistance.