For nearly two decades, North Korea has regularly scared the world with its determination to become a fully fledged nuclear weapons state. On Tuesday it took another decisive step on that road. It conducted its third underground nuclear test, this time with substantial explosive power. It claimed to have successfully miniaturised the device that was used, a key step towards fixing a warhead to a ballistic missile. Once again, North Korea took a bow as the only country in the world that is conducting nuclear tests in the 21st century.

With this act, the country’s young leader Kim Jong-eun has again defied hopes that he might lead an engagement with the outside world. Why he is choosing bombs over butter is unclear. He may want to reinforce his domestic position and assure the North Korean military that it is not being sidelined. He may want to show some of the world’s rogue states – such as Iran – that his nuclear kit works and they might like to buy some off the shelf. He may believe that this display of strength will force the US and others to cave in and negotiate. If so, this is a strange way to approach matters – and a serious misjudgment.

How should the world respond to this latest outrage? As ever, the UN Security Council will convene to consider more sanctions. Some will argue that the US should keep open the possibility of talks with North Korea, however hard that is to stomach. But more than ever, it is China – and in particular Beijing’s new leader Xi Jinping – who holds the key to urging North Korea on to a new path.