A nation’s standing in the world is hard to measure, and change is not always obvious from the inside. To get a sense of perspective, try holding British Prime Minister Theresa May’s appearance at the G20 summit in Hamburg today against the memory of a similar event eight years ago.

The comparison is a little unfair because the 2009 meeting was in London. Gordon Brown, as the hosting prime minister, loomed large over the proceedings. But Brown also made that G20 gathering matter by an exertion of political will. He travelled the world and worked the phone, corralling his international peers towards a deal — a trillion-dollar stimulus for a world economy still reeling from financial meltdown.

Ramachandra Babu/©Gulf News

Fondness for the Brown years is a niche sentiment in British politics, but only the churls deny that he was a substantial figure. When economic crisis struck, he had the gravitas to make world leaders listen.

That already feels like a remote era. For one thing, in former United States president Barack Obama, the White House had a figure capable of projecting moral authority in the world. When President Donald Trump travels to Europe, by contrast, his hosts can only hope that the US president’s impulses don’t spill into sabotage of western alliances.

May’s challenge is to overcome damage already done by the low-level diplomatic vandalism inherent in Brexit. The political genesis of the decision to quit the European Union (EU) may have been different from that of Trump’s election, but it belongs to the same historical disruption. They are the terrible twins, born in ballot-box insurgency in 2016. And here’s the thing: Both were feared, at first, by fellow democracies as symptoms of a dangerous and contagious new populism. Now both look more like horrible accidents of circumstance — ballot-box mutations that earn pity for the nations that produced them.

Brexit clouds everything May says in a miasma of unreliability. It is diplomatic halitosis. The prime minister will advertise United Kingdom’s ambitions for free trade, security cooperation and tackling climate change. It won’t mean anything before the terms of departure from the EU are settled, because the club of European powers is where her capacity to influence those matters has until now been amplified. Had there been much truth to the Eurosceptic portrait of a benighted Britannia crushed under the Brussels yoke, Brown would have been the wallflower at his G20 summit and May the broker of deals in Hamburg. There would be a queue of leaders, eager to ingratiate themselves with a country on the threshold of magnificent liberation.

Some governments do indeed see opportunities in Brexit, but those calculations flow from competitive relish at the prospect of the UK and the EU diminished by the whole business. The Kremlin, for example, will be glad if European nations end up less organised in their opposition to Russia’s meddling in the affairs of its western neighbours. Russian President Vladimir Putin is not so crass as to express public gratitude to British Eurosceptics for their work in undermining the foundations of western liberal democracy. For Nigel Farage, Boris Johnson, Michael Gove and the rest, the sight of authoritarian swagger emboldened around the world must be its own reward. Still, they can take some credit for the spectacle of Trump marauding through the US Constitution, leaving no protocol unviolated.

Their Brexit did not beget Trump, but there is a genetic link. The EU referendum demonstrated the insurgent potential of a campaign that mobilised economic and cultural grievance against a remote political elite. The Leave campaign pioneered the tactics of flagrant mendacity and racially charged nationalism — promising things that were unavailable and stoking fear of immigrant hordes. It made a virtue of despising expert opinion, and discrediting independent analysis as the slippery jargon of a self-serving establishment. Trump, as we know, called himself “Mr Brexit” and invited Farage to be his support act at a rally in Mississippi.

Many Tory Eurosceptics who had disliked the United Kingdom Independence Party’s approach to the referendum, either because its style was vulgar or its xenophobia explicit, had their heads turned by the result of the presidential poll. It triggered a fantasy of rolling revolution, leading perhaps to the unravelling of the EU and a new world order. Britain would be Prometheus among nations — the first to take freedom’s fire.

But that phase hasn’t lasted. The spark did not leap the Channel. Many Europeans saw the electoral shocks of 2016 as cautionary tales, not inspiring parables. Extreme nationalists were hemmed back in French and Dutch elections. German Chancellor Angela Merkel is in good shape to defend her position when Germany votes this autumn. Britain’s electorate had its say on May’s embrace of Brexit as an evangelical march.

The EU referendum and US presidential election were huge events of enduring global consequence, but both have now lost some of their epic quality. Brexit and Trumpism: Neither now seems like giant moments for geopolitics. May’s agenda is indulged, but out of respect for the democracy that dictated it. America’s colossal power demands deference, as always. But there is no longer the hope that Trump’s tyrannical-toddler temperament masks some more sophisticated analysis. The truth is out: There is no credible plan to make America great again.

Buried too are the Brexit promises — not just extra money for the National Health Service, but the myth of a sovereign renaissance. The Leavers’ tone, once so expansive, has shrivelled, now pinched and defensive. Eurosceptics still chant that Brexit must be done, come what may, but now they struggle to make it sound an exciting act of destiny. Brexit is shrinking. The options are fewer, the horizon is narrowing. And May will feel it in Hamburg, where she will be welcomed as the leader of a great country that has chosen to make itself smaller. And so the West is doubly diminished.

— Guardian News & Media Ltd

Rafael Behr is a political columnist for the Guardian.