A day after North Korea paraded its huge and growing military might on the anniversary of the birth of its founding father Kim Il-sung, the country’s latest missile test ended in failure. Yet that will provide little comfort for an anxious watching world; it will only reinforce his grandson Kim Jong-un’s determination to become a fully fledged nuclear power. Despite some false starts, that chilling prospect is a real one.

At one level, the current war of words between the United States and North Korea is nothing new. But after Donald Trump’s arrival on the world stage, the calculus has changed. We now have two maverick, unpredictable, largely untested leaders with a finger on the trigger. A second Korean War, with the US taking out North Korea’s nuclear testing sites and the country retaliating against South Korea, cannot be dismissed. The world is arguably at its most dangerous moment since the Cuban missile crises of the early 1960s.

It is true that Mr Trump’s predecessors shied away from military action against the rogue regime. But his recent actions in Syria and Afghanistan suggest that he might be different. The visit by Mike Pence, the US Vice President, to Seoul, and the “armada” sent by Mr Trump to Korean waters, are unlikely to lower the temperature.

South Korea responds to North Korea's failed missile launch

Let us hope that wise heads prevail. China could play a key role and Mr Trump, having dropped his threat of economic war against Beijing, hopes that in return China will use its unique position to increase the pressure on Pyongyang. If North Korea returned to the negotiating table, Mr Trump could claim that his brinkmanship had worked. But he is playing with fire.

A trigger-happy US President means instability for the West. Mr Trump may have U-turned on his declaration that Nato is obsolete, but its other 27 members hardly have cause for celebration. They have little idea what the man who said he would not be the world’s policeman will do next now he has appointed himself to the role.

They will be concerned that a president who appears to act on a whim, or on what he sees on Fox News, appears to lack a coherent foreign policy. When the dust settled in Syria and Afghanistan, did his bombs really change much? There are concerns that even the mighty US could struggle to fight on three fronts at once – against Isis in Syria and Iraq; in Afghanistan; and now possibly in North Korea.

Donald Trump says Nato 'no longer obsolete'

Does the UK have any role, other than as a cheerleader for Mr Trump? Newspaper reports suggest that Britain has been briefed by the President’s military advisers about a possible pre-emptive strike to eliminate North Korea’s nuclear programme using conventional weapons. Perhaps such reports reflect a desire in the UK Government to be a player in the game.

But despite its permanent seat on the United Nations Security Council, Britain may be less influential in our uncertain new world than it would wish. Its limitations were displayed when Foreign Secretary Boris Johnson failed to win the backing of France, Germany and Italy for further sanctions over Russia over its support for Syria’s Bashar al-Assad.