“It was the blood and flesh of contemporary art that really got my interest,” says Uli Sigg, Swiss businessman, former ambassador to China and North Korea, and reputed to be the largest private collector of contemporary Chinese art in the world. In 2012 he gave 1,463 works from that collection to Hong Kong’s M+ museum, valued at $163mn, and sold them another 47 for $23mm. He owns another 900 works of art and is still acquiring.

He is talking to me from his 17th-century Mauensee castle, which sits on a private island on Mauensee lake, near Lucerne in Switzerland. Sigg, 77, is sitting in a wood-panelled room, wearing an open-necked check shirt. His grey hair is cropped short and there is something of a bird of prey about him, but also joviality and friendliness. Behind him is a series of coloured canvasses, each with text.

“They carry slogans used by banks before the international financial crisis, they were used in advertising, even in the Financial Times!” (“Times are changing; we’re ready,” says one.) The works are parodies by the Chinese artist Chen Shaoxiong from 2009. “But of course the ads completely disappeared, almost overnight, during the crisis.”

Sigg’s interest in contemporary art started when he was student in Zurich; the first work he bought was a Surrealist painting by a Swiss artist — “It was cheap — I didn’t have any money at that time!” He was more focused on rowing than art, indeed he was a Swiss champion aged 22 and his strongly competitive, high-energy side has been evident since even in his collecting.

After a PhD in law from Zurich university, he went to the Middle East and worked as a journalist until his expertise on the region attracted the Swiss elevator company Schindler. “I actually sold a beautiful escalator with just two gilded steps for the Saudi king’s palace,” he laughs. The company sent him to China in 1977 and Sigg set up one of the first foreign joint ventures there.

During those early years he was closely observed by the authorities, but he says: “I knew there must be another reality than the one I was allowed to see, and I thought contemporary art would help me to see it. But I found out it didn’t exist. There was absolutely no art except socialist realism, and later the first experiments were very derivative of western art.” The change came when Deng Xiaoping opened up the country after 1978. “In visual art, that meant that artists could for the first time make independen works.” Previously artists had waited for commissions rather than risk anything else.