As if games that are responsible for so much simple human happiness require any further justification.

Not that sport is incapable of doing good in a broader sense: as a universal idiom, a vehicle for building bridges between people of profoundly different backgrounds, nothing else comes close.

But sport’s power to change the world usually seems most convincing when activated by something spontaneous, rather than a premeditated, top-down brand-building exercise.

A particularly good example of this occurred in Nagoya, Japan exactly half a century ago.

On 4 April 1971, Glenn Cowan, a teenage member of the United States table tennis team competing at that year’s World Championships, managed to find his way onto the Chinese team bus.

This was a time of minimal contact between the two nations, with a form of cold war raging since the Chinese Communist Party takeover in 1949.

As recounted by Jung Chang and Jon Halliday in their gripping biography of Chinese leader Mao Zedong, Mao – the Unknown Story, the Chinese athletes, among the first to travel abroad since the Cultural Revolution began five years earlier, had been given clear instructions on how to treat their US counterparts: this meant no handshakes and no initiating conversation.

In spite of this, one member of the Chinese party, Swaythling Cup-winner and 1971 men’s doubles silver medallist Zhuang Zedong, greeted Cowan.

Photographs of the two men shaking hands appeared in the Japanese press.

Amazingly, as it seems today, within weeks of this small gesture, détente between the two old adversaries was in full swing, leading to a warming of relations that has only really gone into reverse in the past few years, as China has emerged as a serious challenger to US economic hegemony.

How could such a random encounter, a flutter of the butterfly’s wing if you will, alter the course of world affairs so significantly and at the cost, seemingly, of so little effort?

In a word, timing: it turns out US President Richard Nixon and Mao had each been flirting with the idea of a rapprochement for a while.

Nixon was on the hunt for a landmark foreign policy success to distract from the disaster of Vietnam before seeking re-election in 1972; Mao, according to Chang and Halliday, was looking for a way to relaunch himself on the international stage.

The two sides had established secret communications channels, and on 11 January 1971 a message to the effect that Nixon would be welcome to visit Beijing was received in Washington, according to Robert Dallek’s book Nixon and Kissinger - partners in power, through the Romanian ambassador.

Both sides were also extremely cautious, however; a spark was needed to create the sort of positivity that might counter the legacy of more than two decades of glacial relations.

That encounter on the bus, reinforced by the more deliberate sporting contacts which swiftly followed, struck precisely the right chord.

As Chang and Halliday recount, Mao was delighted with Zhuang’s initiative, describing the athlete as a "good diplomat".

Even so, he originally went along with a Foreign Ministry recommendation not to extend to the US players a pre-existing invitation to a number of foreign teams to come to China immediately after the World Championships.

A remarkable passage in the book then describes how the 77-year-old leader changed course late one evening after a quiet dinner and a "large dose of sleeping pills".

Drawing on the account of Wu Xu-jun, Mao’s nurse-cum-assistant, the authors describe how after he finished eating, he slumped on the table before mumbling something.

"It took me a long time to work out that he wanted me to telephone the Foreign Ministry," Wu is quoted as saying - "Invite the American team to China".

The quote continues: "I was dumbstruck.

"I thought this is just the opposite of what he had authorised during the day!"

From that point, events simply charged ahead.

By April 15, the banner headline in the Daily Mirror, the British newspaper, read "Hello China!".

This marked Nixon’s easing of trade and travel restrictions, and the restoration of the direct telephone link between China and Britain "cut off by the Communists when they took over in 1949" – albeit at an eye-watering £1.25 ($1.72/€1.44) a minute.

The story continued: "The US President’s attempts to accelerate the thaw between the Communist giant and the Western world came as America’s table tennis team were being feted in Peking."

Chinese Premier Zhou Enlai was said to have told the US players that their visit had opened "a new page" in US-Chinese relations.

Zhou was even said to have "discussed the hippie movement" with Cowan "who has caused a stir with his long hair and colourful clothes".

The Illustrated London News dated 1 May 1971 ran a spread including a photograph of team captain Jack Howard "with Mao’s Red Book at Kennedy airport on the team’s return".

Wherever they went in China, the accompanying text observed, the players were "greeted with unreserved enthusiasm and were allowed to lose only by a narrow face-saving margin when taken on by their much stronger Chinese opponents."

As Howard told NPR on a return visit to China 35 years later: "We didn’t understand how important it was…

"It really did help improve relations between China and the United States.

"That was the important thing and the lasting thing – and I’m very happy to have been a part of that."