While Donald Trump was toasting Queen Elizabeth II and speaking of the longstanding ties between the US and the UK as “the greatest alliance the world has ever known”, nearly 2,000 miles away, in Moscow, two other global powers were forging their own special relationship – one that will have profound, long-term consequences for the rest of the world.
At the Saint Petersburg International Economic Forum, President Vladimir Putin of Russia hosted China's President Xi Jinping. Mr Xi's praise was effusive. "I have closer interactions with President Putin than with any other foreign colleagues. He is my best and bosom friend," he said.
Alongside the estimated $20 billion of trade deals signed in Russia and rising technological and military links – China's much-maligned telecoms giant Huawei will develop a 5G mobile network in Russia – it is clear these are not just uncommonly affectionate words.
From one perspective, this deepening relationship is a response to US pressure.
Mr Trump's trade war and Washington's efforts to stop allies using Huawei’s technology give the appearance of a broader attempt to marginalise China. Russia, indefinitely suspended from talks by the G7 bloc of nations over its annexation of Crimea in 2014, needs allies. Indeed, it was Mr Putin, not Mr Xi, who most fiercely attacked the US stance on Huawei, calling it “the first technological war of the emerging digital era”.
But the China-Russia alliance is more than that. It is a way of spreading their own messages in a world in which the balance of power is shifting.
Both have been on this trajectory for years. In the military sphere, they co-operate closely, performing joint exercises, while Russia has also sold advanced weaponry to the Chinese. The year before Donald Trump was elected president of the United States, Russia surpassed Saudi Arabia as China's largest oil supplier. Construction of the Power of Siberia pipeline, which will take billions of cubic metres of gas to China every year, commenced in 2012. As recently as January, the US director of national intelligence Dan Coats warned that the two countries “are more aligned than at any point since the mid-1950s”.
Commerce ties it all together. Two years ago, bilateral trade passed $100 billion. Russia and China are hoping to double that by next year. Yet the real prize they both seek is even bigger. It is, in fact, the fragmentation of the US-led global order.
At the Saint Petersburg forum, Mr Putin spelled it out. “New economic centres have emerged and the role of regional currencies has risen,” he said, with the dollar becoming “an instrument of pressure by one country on the rest of the world”.
What Mr Putin meant is something that has been discussed for decades in the developing world: sidelining the US dollar as the global reserve currency. The dollar’s current status places immense power in the hands of Washington to weaponise money flowing through its banks by targeting dollar payments. This power has regularly been deployed by the US against its enemies.
A new reserve currency is some way off, and neither the Chinese renminbi nor Russian rouble is in a position to usurp the dollar, but both nations see the benefit of reducing their dependency on it. Five years ago, China and Russia signed a range of energy and trade deals that would be financed by a currency swap, bypassing the need for US currency. However, the overwhelming majority of trade between the two is still conducted in dollars.
If China and Russia could usurp the dollar and handle the American response, it would send a signal to other countries that increasing their stores of foreign reserves in other currencies, or seeking currency swaps, would not provoke an immediate US backlash.
In foreign affairs, they also have common goals. Both hold veto power on the UN Security Council and often work in concert, balancing the tendency for the US and the UK, who also hold veto power, to vote together.
The two have common positions on some key foreign policy questions, for example disliking western-led attempts to oust Bashar Al Assad in Syria and Nicolas Maduro in Venezuela. They also wield increasing power over dangerous flashpoints, such as North Korea. For all the media attention lavished on Mr Trump's two meetings with Kim Jong-un, it is Beijing that has the most influence over Pyongyang. Two months ago, Mr Kim met Mr Putin in Russia for the first time.
Yet for all their commonalities, a China-Russia alliance is fundamentally a marriage of convenience. And while both are geopolitical allies now, they could easily become rivals in the future.
There is past precedent for this. The close alliance forged in the 1950s between the Soviet Union and a newly communist China began to fall apart less than a decade later. Ideological differences about the future of communism and vastly different internal conditions – in 1950, China's population was more than five times the size of Russia's; today, it is nearly 10 times as big – precipitated the split.
Today, China is well on its way to becoming a global superpower, with commensurate economic and military might. Russia, while an important military force, suffers from a drastically underperforming economy and a shrinking population. Alone, these factors are enough to create major differences of perspective and opinion.
If, when and how the cracks start to show will be affected by how the US chooses to respond to Russia and China's growing relationship. Political decisions from Washington could prise them apart, or push them together. After all, both sides have much to gain – and some marriages of convenience last a long time.