To my mind modern Britain stands upon 2 pillars of strength, each pillar powerfully influenced the outcome of World War II. The first, the abdication of King Edward VIII, Hitler's King in Waiting. Perhaps the greatest single event in the history of England. The abdication not only brought Bertie to the throne but perhaps more importantly his wife, the steely Queen Elizabeth. I attribute David's post war survival to the innate kindness of the English people and that they were simply tired of death. He and Wallis would have been strung up in most non-English speaking countries.
Kings no longer lead armies into battle but they can and often do lead the people. Bertie and Elizabeth's wartime example, staying in London and sharing the day to day suffering of the locals was a needed tonic to a country at war, and one they would have never gotten from Bertie's predecessor.
The second, and perhaps just as unlikely to predict as the abdication, was Winston Churchill's 1940 invitation from King George VI to form a government as prime minister. Churchill had, at best, a checkered history in politics, was distrusted by both Labour and the Conservatives, but the only armed service actively preparing for the coming war was Winston's Admiralty . On this date in 1940 Winston took on the role he prepared for his entire life. " I was conscious of a profound sense of relief" he later wrote, "At last I had the authority to give directions over the whole scene. I felt as if I were walking with destiny, and that all my past life had been but a preparation for this hour and this trial."
World War II history is difficult to imagine without him at the helm.