Britain’s new PM should abjure his dangerous brinkmanship in seeing Brexit through

Boris Johnson, Britain’s new Prime Minister, has achieved one of his life’s ambitions. His defiant speech at Downing Street on Wednesday, pledging a “no ifs, no buts” exit from the European Union before October 31, is clear indication that he will pursue a hard Brexit. “Doubters, doomsters and gloomsters,” would be defeated, he declared in characteristic style. Several ministers from the previous government, who have either resigned or have been dropped, are all presumably among them. Conversely, the induction of several eurosceptics, most notably Jacob Rees-Mogg from the European Research Group, leaves no doubt that the Johnson team is nothing if not a Brexit cabinet. The other is Dominic Raab who, during the Conservative leadership race, advocated proroguing Parliament to ensure MPs did not stop a no-deal exit. Mr. Johnson’s rhetoric is reminiscent of Theresa May’s uncompromising early stance that no deal was better than a bad deal. While she was forced to back down from several unrealistic positions, Mr. Johnson’s place in Downing Street is far more precarious than her’s. His majority in the House of Commons could drop to just two seats if, as the polls forecast, the Tories lose the by-election in August. This arithmetic is crucial in what is a sharply polarised Parliament now. Party hardliners have threatened to vote out the government if the exit deadline was breached for a third time. With Brussels ruling out a renegotiation of the withdrawal agreement, the chances of leaving on October 31 seem remote.

Mr. Johnson has for too long painted the other 27 nations in the bloc as hostile adversaries that have undermined Britain’s sovereignty. He has paid scant regard to mounting evidence, most recently from the International Monetary Fund, of the crippling economic impact of Britain leaving the union. Mr. Johnson has even dismissed the risks to the integrity of the Good Friday agreement between the U.K. and Ireland, in the absence of the prevailing soft borders connecting Dublin and Belfast. But as Prime Minister he can ill-afford to indulge the populist instincts of the narrow nationalists among the Conservatives. Instead, he must reckon with the real and grave consequences for the nation and even his party, of abruptly walking out on London’s closest partners. The contradictions of that approach were laid bare this week in London’s bid to coordinate with Brussels to protect European commercial shipping in West Asia. Clearly, London’s interests lie in redoubling efforts to resurrect the multilateral order that U.S. President Donald Trump seems so keen to undo. The special relationship between the principal trans-Atlantic partners is nothing if it did not encompass a more universal vision. Mr. Johnson must abjure his dangerous brinkmanship. That would be in Britain’s interest.