Sir Nevile Meyrick Henderson, KCMG, PC (June 10, 1882 - December 30, 1942) was the Ambassador of the British Empire to Germany from 1937 to 1939. He believed that Adolf Hitler could be controlled and pushed toward peace and cooperation with the Western powers. In February 1939 he cabled the Foreign Office in London: "If we handle him (Hitler) right, my belief is that he will become gradually more pacific. But if we treat him as a pariah or mad dog we shall turn him finally and irrevocably into one."
Henderson was ambassador at the time of the Munich Pact, and counselled Neville Chamberlain to enter into it. "When [German Foreign Minister] Joachim Von Ribbentrop refused to give a copy of the German demends to the British Ambassador at midnight of August 30-31 , the two almost came to blows. Ambassador Henderson, who had long advocated concessions to Germany, recognized that here was a deliberately conceived alibi the German government had prepared fr a war it was determined to start. No wonder Henderson was angry; von Ribbentrop on the other hand could see war ahead and went home beaming."
Shortly thereafter, he returned to London for medical treatment, returning to Berlin in ill-health (he would die of cancer less than four years later) in February 1939 ().
During the course of 1939, Henderson came into frequent conflict with Alexander Cadogan, Permanent Undersecretary of the Foreign Office. Henderson argued that Britain should go about rearmament in secret, as a public rearmament would encourage the belief that Britain planned to go to war with Germany. Cadogan and the Foreign Office disagreed.
While advising accommodation over Germany's territorial ambitions in Poland - as he had in Czechoslovakia and Austria - it was Henderson who delivered the ultimatum on the morning of September 3, 1939 to Hitler stating that if hostilities between Germany and Poland did not cease by 11 a.m. that day, a state of war would exist. Germany did not respond, and Prime Minister Neville Chamberlain declared war at 11:15 a.m.
After returning to London, Henderson wrote a book, Failure of Mission: Berlin 1937-1939, published in 1940. In it, he spoke highly of some members of the Nazi regime, including Hermann Goering. In contrast, he was not complimentary about Joachim von Ribbentrop.