“The Tories, in their terror, have elevated a cavorting charlatan to the steps of Downing Street.”

Those are the words of Sir Max Hastings, writing in The Guardian on June 24. Hastings is the former editor of The Daily Telegraph, the conservative British newspaper that has loyally backed the Tory party for generations. Like many other Tories — and ex-Tories — Hastings is grappling with the likelihood that former foreign secretary Boris Johnson, now one of two remaining candidates, will be Britain’s prime minister when the 160,000 party members vote on July 22 for a new leader. “His elevation,” Hastings writes, “will signal Britain’s abandonment of any claim to be a serious country.”

The list of other old friends and colleagues willing to denounce Johnson — or else just to laugh at him — is not short. A journalist who worked with him: “The Johnsonian creed [is] that it is, in his own words, acceptable, sometimes desirable to lie.” A colleague from the Foreign Office: “The more he repeats what everyone can see is not credible, the more his own credibility disappears.” Another: “The worst foreign secretary we’ve ever had.”

I have worked for Hastings and have known Johnson for almost 30 years. And I am quoting other people who have known Johnson for a long time for a reason. Because the fact is that all of them — all of us — knew that he exaggerated stories or else just invented them.

Hastings employed Johnson as the ’s Brussels correspondent, tolerating him for years as he portrayed the European Union as a font of regulatory madness, writing amusing articles with titles such as “Threat to British pink sausages” or repeating false rumours that British bureaucrats were going to ban double-decker buses. Although scoffed at by those in the know, these tall tales had an impact, helping to build the distrust for the EU that eventually led to Brexit.

Johnson was aware of the impact, and relished it. “I was sort of chucking these rocks over the garden wall and I listened to this amazing crash from the greenhouse next door over in England,” he told the BBC years later, “as everything I wrote from Brussels was having this amazing, explosive effect on the Tory party — and it really gave me this, I suppose, rather weird sense of power.”

The “amazing crash” in London also sold newspapers, which is part of why Johnson was tolerated for so long. But there was a deeper reason, too: the not-entirely-accurate stories appealed to nostalgic conservatives who resented the idea that Britain, no longer an empire, had to exert influence in the world by exerting influence in Brussels. Johnson had identified a powerful, disgruntled audience, and he fed their discontent.

Later, as Mayor of London, Johnson reversed his outlook: he reinvented himself as a champion of a cosmopolitan city, integrated with Europe in the world. About a year before the European referendum campaign, he told me that Brexit was a bad idea, that London was against it and that it would not happen. Famously, in 2016, he changed his mind. He knew that the anti-European movement he had done so much to create had captured the Conservative Party. He must have seen that to become the Tory leader — and, thus, prime minister — he would have to appeal again to that deep nostalgia. And so he did.

It is in this sense — and not, actually, in many others — that Johnson resembles Donald Trump. For Trump is also someone whose fibs and short cuts were tolerated for many, many years by the people around him. New York bankers knew that his businesses were dodgy and refused, after a while, to lend him money. New York tabloids knew that he invented stories and sources. His own ghostwriter has said that The Art of the Deal, Trump’s 1987 bestselling memoir, is counterfeit. Trump is no good at deals and never has been.

But Trump, like Johnson, got away with it. The lies sold newspapers; they also satisfied a New York stereotype: the brash, vulgar-yet-successful businessman who so many imagine they might some day become. He got away with running a fake charity, with promoting business scams, with a bogus “university” because a certain audience found all of that appealing — and because no one bothered to call him out.

After Trump became president, it was really too late to investigate his dodgy investments in Azerbaijan or his links to Russian money laundering. Those stories should have eliminated him from business, and from public life, long before 2016. By the same token, it is too late to describe Johnson as a “charlatan” or a fantasist given that the Telegraph, the Conservative Party and the Foreign Office tolerated him for three decades. Johnson is not the cause of British unseriousness. He is, rather, the product of institutions that stopped behaving seriously a long time ago.

• Anne Applebaum is a Washington Post columnist, covering national politics and foreign policy, with a special focus on Europe and Russia. She is also a Pulitzer Prize-winning historian and a professor of practice at the London School of Economics. She is a former member of The Washington Post’s editorial board