Peace with North Korea? Then war with Iran? Even by the standards of Donald Trump, the Washington kaleidoscope is turning dizzyingly fast. The US president says he wants a deal with Pyongyang to scrap its nuclear weapons. He is also minded to shatter international trust in American leadership by reneging on the nuclear pact with Iran. The contradiction is wilfully scorned. This is not the way to halt the global slide towards nuclear proliferation.

The remarkable thaw in Mr Trump’s relations with Kim Jong Un’s North Korean regime has confounded predictions. Only months after the two leaders were exchanging volleys of threats and insults, the talk is now of denuclearisation of the Korean peninsula and a permanent peace treaty.

With accustomed modesty, Mr Trump muses he may end up a recipient of the Nobel Peace Prize.