A brief meeting between a German and a Danish physicist in Copenhagen in 1941 might seem the flimsiest of constructs for an entire theatrical drama.
Not least, because the meeting was cut abruptly short and recollections of what was and was not discussed are clouded in ambiguity.
But make no mistake - there is nothing insubstantial in Michael Frayn’s forensic retrospective examination of that brief social interaction between Werner Heisenberg (Charles Edwards), Niels Bohr (Paul Jesson), and Bohr’s wife Margrethe (Patricia Hodge).
As the three protagonists constantly re-evaluate that moment in time desperately seeking to make sense of it, the first real glimmer of its significance comes when they consider how things might have changed had the meeting run its full course.
Spoiler alert - but one possibility is that Germany could have beaten America to the atomic bomb; that London or Paris or even Copenhagen could have been obliterated; and the world as we know it today might be entirely different.
Frayn concedes that new evidence since the play was first produced in 1998 might have persuaded to him write things differently. But probably only at the margins.
Instead, he is unstintingly faithful to the scientific conversations that would have taken place - exploring everything from quantum mechanics to theoretical physics. The only concessions he makes to the audience is allowing the explanations to be given in relatively simple terms for the alleged benefit of Margrethe and inserting some human dimension to the lives of these learned giants.
For those wanting to catch a glimpse of real life meetings, Love Island and Big Brother it certainly isn’t. Nor, despite the perfectly accented humour from the formidable Hodge, is it the Big Bang Theory.
But for those in the audience who are prepared to persevere there is the reward of the huge emotional sweep gaining momentum throughout the second half, observing three actors at the top of their game - and the stark realisation that no-one in the theatre might be there had it not been for one brief meeting in Copenhagen at the height of the second world war.
Copenhagen - Minerva Theatre, Chichester