Oscar-bound movie with a primitive plot. Gary Oldman is brilliant and totally believable in imitating Churchill's physicality but that's about it. Kennedy once quipped: "What is private is policy. What is public is propaganda." The movie substitutes Churchill's patriotic speeches and corny flag-waving scenes, probably invented, for his political maneuvers and shenanigans. His refusal to negotiate with Adolf is cursorily explained in the movie "you don't negotiate with a lion having your head in his mouth" but this line is never bolstered by cinematic means.
In fact, Churchill was not a naive fulminating every time his German counterpart was mentioned but a very practical politician who lived through German trashing of Munich agreements (which he supported), attacking Poland and kidnapping British intelligence personnel from then neutral Holland (Venlo Incident), which could have impressed him more than the two previous episodes. Nor was he a passionate anti-Nazi--after the WWII he contributed to the legal defense of Nazi war criminals in British custody. He simply understood that if Adolf disregarded all previous agreements and understandings--probably a generic feature of German diplomacy from Friedrich II to Merkel--he will not stop now with victory seemingly in his grasp.