It was a moment of mortal peril. Britain reeled from a series of devastating military defeats. Its politicians faced one of the most monumental decisions in 20th century history. Faced with a rampant Germany on the continent led by the fascist dictator Adolf Hitler, should Britain fight? Or make peace? In Parliament the debate raged, ultimately ending in the emergence of one man who would guide Britain to victory from the jaws of defeat: Winston Churchill. For the 80th anniversary of Britain's darkest hour Dan Snow visits the House of Commons to learn about the speeches that turned the tide of the Second World War.