LAURENCE REES: What about the relationship with the Americans? If Roosevelt hadn’t wanted to progress a form of military alliance, even unofficially, during that period,  what would have been the consequences for Britain? How important was that relationship in 1940 with America?

ANDREW ROBERTS: It was very important to have a close relationship with America and we were always attempting to draw the Americans in more closely. I think exaggerating the threat of invasion was also something that went down very well in America and we didn’t baulk at anything really, in terms of propaganda, to try and get the Americans on side. Of course we got very little from them, they had a general election in the November of 1940 and so there was no chance of having anything particularly useful. The Destroyers for Bases deal is a hard fought historical issue. Was it really helpful to us to have lots of obsolete destroyers? In a sense it might have been because they took the place of some, and they freed up other, useful, destroyers that we were able to use. But it was more of a sign of their willingness, and in many ways the Americans were being genuinely helpful in taking over patrolling parts of the Atlantic that we were overstretched in. So yes it was very important, but it was also again something for morale, Churchill mentions it again and again, that the new world will come to the saviour of the old. These are not just rhetorical phrases, they actually give people hope.

LAURENCE REES: Looking at the relationship between Churchill and FDR, it’s clear isn’t it that it was nothing like as sweet and happy as the propaganda at the time made out?

ANDREW ROBERTS: It was in the interests of both men to make out that these two people were firm friends, but that’s not the case. They were very highly attuned politicians who at every stage of the war put the interests of their own countries first, and that’s what you elect the President or Prime Minister to do. It is perfectly understandable. They did get on fine amongst themselves, but they never allowed the myth of their personal chumminess to get in the way of business.

LAURENCE REES: But, in fact, in terms of personalities and political beliefs these two people aren’t likely to get on are they? Aren't there a whole series of political issues that divide them?

ANDREW ROBERTS: They have a bit in common in terms of both being aristocrats in their own countries, but really there is nothing politically to hold Churchill to Roosevelt and visa versa, and that becomes very clear by about 1944 when there’s absolutely no threat of losing the war and everybody’s looking forward to the post war world. Churchill’s vision and FDR’s are not just not the same, and this leads to clashes between them. For a 3 month period after October 1944 Roosevelt hardly answers letters from Churchill. There are 200 more letters that Churchill sends to Roosevelt than Roosevelt replies to. At the same time small things that shouldn’t really matter, like the future governance of small pacific islands and civil aviation rights and things like that - Argentinean beef - these were things that when the two people were getting on well wouldn’t have raised a cloud. However, they become really quite serious issues between the British and the Americans because the two paths are diverging. In fact at one stage Eleanor Roosevelt told the Former Post Master General of America that FDR had preferred Stalin to Churchill.