"For a couple of days in May 1940, the fate of the world turned on the fall of a leaf" says John Gray. He outlines the strange conjunction of events - and the work of chance - that led to Churchill becoming Prime Minister.

He muses on how Churchill was found by one of his advisers around one o'clock on the morning of May 9th "brooding alone in one of his clubs". He was given a crucial bit of advice which may have secured him the job. What would have happened Gray wonders if he hadn't been found and that advice - to say nothing! - not been passed on?

He also ponders whether it was it Churchill's recurring melancholy which made for his greatness? "It's hard to resist the thought that the dark view of the world that came on Churchill in his moods of desolation enabled him to see what others could not".

"Churchill had not one life but several" says Gray. Without them all, "history would have been very different, and the world darker than anything we can easily imagine".

Producer: Adele Armstrong.