LAURENCE REES: So if this was, as you suggest, from the beginning an ideological war for the British and France - a kind of 'moral crusade' - was this because Hitler had shown himself post-Munich that he could not be trusted and therefore must be stopped?

RICHARD OVERY: No, I think it’s lots of things that feed into this. I think the Spanish Civil War plays an extraordinarily important part in mobilising the opinion of Britain and France. But I think that comes in March 1939 too, [at the same time] as the Prague coup, [and] is just as important for the British and French progressive opinion. Spain has finally fallen into the fascist camp and there’s the threat of Mussolini, Japanese militarism, the chaos of Asia, then of course there’s all the ambiguities in the empire. There are so many different pressures that one could point to, and the British and French had, in a sense, seen themselves as the champions of this kind of liberal diplomacy and liberal imperialism for 40, 50, 60 years. They had fought the First World War ostensibly for that reason and here they are back in crisis again.

Although, of course, you’re right. If Hitler had not done the things he’d done it wouldn’t have been Poland they’d have been choosing as their site of conflict. I think they’d made up their mind that somehow or other some effort had to be made. This is at the heart of Chamberlain’s notion: the grand settlement. Some effort has to be made to bring the world back to its senses, and its senses mean re-establishing Western values, and I think that that is a very important element underlying the British and the French war effort and later on underlying the American war effort. But of course it’s also expressed in terms of the balance of power. The British and French both felt that Mussolini and Japan threatened their empires. You could turn that round and argue that Hitler did the same and so on, and of course the Americans felt profoundly threatened by Japanese imperialism in the Pacific. So of course there’s 'raison d'État' as well, nobody would argue that didn’t exist. But I think those historians who have tended to explain all the circumstances that lead from local war to European war to world war in strategic studies terms miss out what seems to me to be much more important for many of these people which is the way they view the world and their perception of the values that matter. So I think we need to inject that back into the argument.