Two nuclear-armed states on a collision course with no obvious exit ramp. An erratic Russian leader using apocalyptic language - "if you want us to all meet in hell, it's up to you". Showdowns at the United Nations, with each side accusing the other of essentially gambling with Armageddon.

For six decades, the Cuban missile crisis has been viewed as the defining confrontation of the modern age, the world's closest brush with nuclear annihilation. The war in Ukraine presents perils of at least equal magnitude, particularly now that President Vladimir Putin has backed himself into a corner by declaring large chunks of neighbouring Ukraine as belonging to Russia "forever".