But supposing there is a German guarantee, of what is its value? It is unnecessary to accuse Germany of perfidy. Not only the Nazi Government but all previous German Governments from the time of Frederick the Great downwards have made their position perfectly clear. To them an international assurance is no more than a statement of present intention. It has no absolute validity for the future.

Letter to The Guardian after the Munich Agreement of 1938, as quoted in Plough My Own Furrow (1965) by Martin Gilbert, pp. 416-20