"I use it as an example of how the Chinese economy had grown in 15 years, that it was important enough to ring the ambassador after office hours, to check the story wasn't true," Galsworthy said.

Fast-forward another 20 years, and China's importance on the global financial stage is obvious.

In 2016, the International Monetary Fund included the yuan in its basket of currencies that make up the special drawing rights, boosting its importance as a global reserve currency.

Today, even a minor depreciation of the yuan catches the attention of not just the UK Treasury but also hundreds of bankers and asset managers. After all, in 2016, London overtook Singapore as the second-largest offshore yuan center, just after Hong Kong.

All those changes result from China's reform and opening-up policy, which was launched in 1978 by Deng Xiaoping. Essentially, the policy introduced incentives to private entrepreneurs and opened the Chinese market to foreigners, helping to integrate China with the world economy.

Looking back, Galsworthy uses the words "dramatic, earthshaking, and chaotic" to describe reform and opening-up - "chaotic" in the sense that a lot of the country's market rules and regulations were still playing catch-up with its booming business environment.

He attributes the successful outcome of the reforms to the innate entrepreneurial spirit of the Chinese people, which was not allowed to bloom in the planned economy. "It was as if a great spring had been wound up and not allowed to go," he said. "And suddenly, there was a release."

Galsworthy noticed many changes in the 1980s. Walking into a shop, he would immediately realize that material incentives had been introduced, as shop assistants, previously indifferent, sought to persuade customers to buy.

"The changes were small. At the time we didn't realize how reform would change China in larger ways," he recalled, adding that the full extent of China's economic power only became obvious to the West in the 21st century.

"That realization, that China is going to be one of the major economies in the world, only came this century. The changes are dramatic, and it is hard to believe it is the same country."

In the '80s, his involvement with the Hong Kong handover discussions gave him ample opportunities to meet Deng.

"I had the impression of a man who knew exactly what he wanted and who was extremely tough in going for it," Galsworthy said. "He was essentially pragmatic, he believed in results. If you could assure him that the results he wanted could be achieved in many ways, he was flexible on how to get there."

He was also impressed by the way Deng made his views known without speaking. "He used his spittoons very quickly for that purpose. It was all body language."

One famous demonstration of Deng's use of the spittoon happened in 1982, when British Prime Minister Margaret Thatcher visited China and met with Deng to discuss Hong Kong.

At the beginning of the meeting, Thatcher raised the idea of the UK continuing to administer Hong Kong. In reply, Deng spat loudly into the spittoon beside his chair.

On July 1, 1997, Hong Kong returned to China. It was perhaps that "toughness" and "clear vision" in Deng, as observed by Galsworthy, that put China on the right path to reform and opening-up.

Galsworthy said he is glad to see the clear vision, especially in relation to China's further reform and opening-up, continuing under President Xi Jinping, a leader whom Galsworthy describes as "down to earth" and who "says what he thinks".

"I expect China to play an increasingly important role in international affairs," he said. "That's something we always try to encourage."

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