Has Boris Johnson ever done a job well?

LONDON — At the point where the River Thames empties into the North Sea, Boris Johnson wanted to build an airport on an artificial island.

It was 2009, and Johnson was newly in office as London mayor. To study the airport idea, he tried to enlist a leading scientist, professor David King, except King had recently warned about rising water levels on the Thames. Hardly ideal conditions for an airport, he told the mayor, balking at the project while instead offering to look into other uses for the waterway.

So the professor was taken aback when Johnson named him chairman of a team investigating a Thames estuary airport. King confronted the mayor.

“He said, ‘Oh, silly me, silly me,’ or something like that, and fluffed his hair,” King recalled. The mayor went on: “Ah David, it’ll be all right.”

It was not all right. Like several of Johnson’s marquee projects as mayor, the island airport plan sucked up millions of pounds in planning fees but never went anywhere against nearly unanimous opposition and practical hurdles, such as how to put an airport on an internationally protected bird habitat.

Expected to become prime minister this week, Johnson, 55, is deploying the bonhomie and bumbling, confected persona that made him London mayor. He is the darling of rank-and-file Tories hellbent on Brexit. He is the choice of President Donald Trump. He is the ringmaster of a campaign circus that last week featured Johnson punching the air with vacuum-packed smoked herring.

But despite his charm, many of his colleagues, as well as political analysts, question his competence. During his two terms as London mayor, he read the public mood and aimed millions of pounds the same way, whatever dire warnings his briefing papers contained. His most recent highprofile job, foreign secretary, found him ill at ease in a role that required more gravitas than grandiloquence.

The next prime minister will face perhaps Britain’s greatest peacetime crisis, Brexit, one that turns on the sort of labyrinthine details that Johnson so avoids. His promise to extract Britain from the European Union by the end of October has left many Britons worrying that he will send the country hurtling toward a potentially calamitous no-deal Brexit.

Even allies acknowledge that Johnson sees himself as someone focused on the big picture, rather than on the details of governance. He is intuitive and improvisational, allies say, often junking a prepared text when making a speech.

“What he does is he picks up the vibration of the moment, of the day, and then he understands the way to go,” said Ray Lewis, an adviser to Johnson at London’s City Hall.