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There has always been a shared conceit at the heart of the special relationship between the United States and United Kingdom that global leadership is best expressed and exerted in English.

More boastful than the Brits, successive US presidents have trumpeted the notion of American exceptionalism.

Prime ministers, in a more understated manner, have also come to believe in British exceptionalism, the idea that Westminster is the mother parliament, and that the UK has a governing model and liberal values that set the global standard for others to follow, not least its former colonies.

In the post-war Anglo-American order those ideas came together. In many ways, it was the product of Anglo-American exceptionalist thinking: the "city upon a hill" meets "this sceptred isle".

Nato, the IMF, the World Bank and the Five Eyes intelligence community all stemmed from the Atlantic Charter signed by Franklin Delano Roosevelt and Winston Churchill in August 1941.

The liberalised free trade system that flourished after the war is often called the Anglo-Saxon model. The post-world global architecture, diplomatic, mercantile and financial, was largely an English-speaking construct.

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In recent weeks, however, the Anglo-American order has looked increasingly weak and wobbly. The unexpectedly messy result of the British election makes it look still more fragile, like a historic edifice left tottering in the wake of a major quake.

There is uncertainty in Westminster, and something nearing chaos in Washington because of Russian probe at the White House and on Capitol Hill.

Neither Britain nor America can boast strong and stable governments. Neither have the look of global exemplars.

In the six weeks since Theresa May called her snap election, the global tectonic plates have shifted fast, leaving Britain and America increasingly adrift.

Donald Trump, during his first international trip, refused to publicly endorse Article V of the Nato treaty and publicly scolded his allies over financial burden sharing.

He found himself isolated at the G7 summit in Sicily. Then, on his return to Washington, came the announcement that the United States would withdraw from the Paris agreement, a decision of massive planetary and geopolitical import.

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Here, America First meant America alone, and Trump seemed to revel in his neo-isolationism - as he did when he withdrew from the Trans-Pacific Partnership early in his presidency.

For Britain, the diplomatic impact of Brexit has also become clearer in recent weeks. EU leaders have bluntly outlined how they will set the terms of the divorce settlement, in what looks more and more like a diktat than an amicable separation.

The 27 remaining members of the EU have also made it clear they intend to penalise the UK.

When Jean-Claude Juncker met Theresa May at Downing Street shortly after she called the election, he was evidently dismayed by her approach.

"I'm leaving Downing Street 10 times more sceptical than I was before," the EU Commission president reportedly informed his host.

As one senior EU diplomat put it to me: "Britain has shot itself in one foot. We intend to shoot you in the other."

The British prime minister, by failing to win an election she didn't have to call, has weakened her bargaining position still further. Brexit negotiator Guy Verhofstadt has already called the UK election: "Yet another own goal."

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In recent weeks it is not only the UK's relations with the EU that have become more strained. Its cherished trans-Atlantic alliance has also been subject to some unforeseen stress tests.

I never expected to report that Britain would stop sharing sensitive intelligence with the United States, but that was the story we broke in the aftermath of the Manchester bombing.

Then, following the London attack, came Donald Trump's Twitter assault on the London Mayor Sadiq Khan. Again, in the pre-Trump world it would have been unthinkable for a US President to mount such a vicious attack on a British mayor in the wake of a UK terror attack.

Sir Christopher Meyer, Britain's former ambassador in Washington, seemed to capture the public mood when he noted: "Trump makes me puke."

The prime minister steered clear of delivering a stiff public rebuke to the President over his attack on Mayor Khan, presumably out of fear of angering Donald Trump and jeopardising a post-Brexit trade deal with the US.

Perhaps this also explained why she didn't join with Germany, France and Italy in signing a joint declaration slamming Trump's Paris decision.

Media playback is unsupported on your device Media caption Donald Trump challenged London Mayor Sadiq Khan to an IQ test

But again that emphasises Britain's weakness. The special relationship has always been an asymmetrical relationship but now it seems even more lop-sided. It speaks of the UK's post-Brexit diplomacy of desperation.

The trans-Atlantic alliance will eventually have to deal with a longer-term problem that will outlast the Trump administration. One of Britain's great uses to Washington in recent decades has been as a bridge to the European Union.

It's why Barack Obama lobbied so hard for a 'remain' vote ahead of last year's referendum. Under future US presidents, it is easy to imagine a German-American alliance supplanting the special relationship.

Voids in global leadership are immediately filled, and we've seen that happen at warp speed over the past few weeks. Brexit has galvanised the European Union. The election of Emmanuel Macron has revitalised the Franco-German alliance, giving it a more youthful and dynamic look.

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Post-Paris, a green alliance has emerged between Beijing and Brussels. More broadly, China sees the chance to extend its sphere of influence, positioning itself on environmental issues as the international pace-setter. Even before Mr Trump took the oath of office, this looked more likely to be the Asian Century rather than a repeat of the American Century.

Europe eyes an enhanced role for itself, too. "We Europeans must really take our fate into our own hands," declared Angela Merkel during a speech in a Bavarian beer hall after the disastrous G7 summit.

In a pointed dig at America and Britain, she also warned that the days when Germany could completely rely on others are "over to a certain extent".

More and more, the German chancellor looks like the leader of the free world, something that would have required a massive leap of imagination in the years immediately after World War II, when the English-speaking liberal global order was taking shape.

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Winston Churchill, during the 1946 speech in Fulton, Missouri, in which he coined the phrase "special relationship" (and also the "iron curtain"), noted: "It is necessary that constancy of mind, persistency of purpose, and the grand simplicity of decision shall guide and rule the conduct of the English-speaking peoples in peace as they did in war. We must, and I believe we shall, prove ourselves equal to this severe requirement."

Right now, both the United States and the United Kingdom seem to be failing that Churchillian test.

These English-speaking nations no longer speak with such a clarion voice, and the rest of the world no longer takes such heed.

A new world order seems to be emerging that is being articulated in other tongues.