When Uli Sigg, a leading collector of contemporary Chinese art, finally announced on June 12th the donation of more than 1,000 works to a yet-to-be-built museum in Hong Kong, he sent an unmistakable message.

The deal helps Hong Kong in its goal to become a cultural centre as well as a financial power. Beijing and Shanghai, brimming with museums too timid to accommodate the most extensive collection of Chinese art of the last 30 years, lost out. The paintings and installations in Mr Sigg's collection, many of them by China’s hottest artists, would run afoul of the censoring authorities on the mainland.

Mr Sigg, a Swiss businessman and former Swiss Ambassador to China, painstakingly amassed the collection while living in Beijing, buying directly from the artists and often driving a hard bargain. He forged a particular friendship with Ai Weiwei, an artist and human-rights campaigner. Of the nearly 1,500 works Mr Sigg said he was giving to the M+ museum, 26 are by Mr Ai. The collection includes all the big names, such as Fang Lijun, Zhang Xiaogang, Li Shan and Yu Youhan. There are newcomers, too, who would otherwise not have a chance to be shown in a museum. Sotheby’s estimated the gift to be worth $165m. The M+ museum is to be built in West Kowloon by 2017.

There has long been speculation about what Mr Sigg would do with his huge collection. Part of the interest has been curiosity about what is actually in the collection. Some of it hangs in Mr Sigg’s home, some of it has toured, but much of it has been in storage in Switzerland.

As new museums in China multiply and existing museums move to grander quarters, the mainland would be the obvious place to showcase the artists who are fetching big prices and building big reputations in the West. But that turned out to be a step too far for censorious China.

“I have discussed it with public institutions in China, and I decided the mainland institutions are not ready yet for such a collection,” Mr Sigg said. Among the obstacles are prohibitions on showing imagery of living politicians, and limitations on sexual images. “We deal with public order everywhere, but in China it’s a very particular public order,” he said.

Along with the gift that covers 310 artists, Mr Sigg also sold the M+ museum 47 of his most valuable Chinese works from the 1970s and 1980s for $177m. He was not parting with everything, he said. Some of his favourites would stay behind in Switzerland for his personal pleasure. Those paintings presumably include the portraits that Mr Sigg commissioned Chinese artists to paint of himself.

The collection is the envy of followers of contemporary Chinese art. Mr Sigg arrived in China in the late 1970s as the chief executive of the Schindler Group, a Swiss manufacturer of elevators. He forged the first joint venture between a Western company and a Chinese partner, setting the template for many businesses that came to China during the opening under Deng Xiaoping. His early arrival gave him a head start on the art scene, which like the economy, was then being liberalised. At first, Mr. Sigg, who had collected Western art in Switzerland, watched but didn’t buy.

Then in the early 1990s he began to buy, sweeping up works to shape a collection designed to closely follow the rapidly changing art scene. In announcing his gift to M+, Mr Sigg said he wanted to document the “art production of China from day one to today—along the timeline, across all media, rather than according to my personal taste as a private collector.”

Along the way, Mr Sigg and Ai Weiwei bonded. When Mr Sigg became Switzerland's ambassador to China in 1995, he continued his buying spree, sometimes guided by Mr Ai, who brought the collector directly to many of the artists’ studios. By the early 2000s, Mr Sigg was able to return the favour. He introduced Mr Ai to the Swiss architects Herzog and de Meuron, and out of that collaboration came the 2008 Olympic Stadium known as the Bird’s Nest.

In a shot aimed straight at the Chinese government, Mr Sigg said this week it would behove the authorities to understand that contemporary art, though often political and critical, had much to offer, even if it did not fit the traditional Chinese view of art as beauty and harmony.