It is 60 years since the Korean peninsula was at the very centre of international affairs. After the Korean war, the focus moved on – to Vietnam, eastern Europe, the Middle East, even to Afghanistan. But Korea now has a good claim to be right back at the centre of global concerns.

North Korea’s tests of nuclear weapons and ballistic missiles this year, as well as its increasingly warlike rhetoric, have made South Koreans and Americans think hard about the previously unthinkable – the possibility that a nuclear war might actually break out on the Korean peninsula.

I spent some of last week at the Jeju forum in South Korea, where researchers, politicians and diplomats grappled with a number of terrifying questions: such as what would the impact be of a nuclear strike on Seoul, the South Korean capital; and could South Korea launch a successful pre-emptive strike on the North’s weapons? (Answers: appalling and no.)