With my partner Pierre de Meuron, I had become familiar with Chinese contemporary artists through Uli Sigg [the Swiss collector of modern Chinese art]. It was through him that we had learnt of Ai Weiwei's work, although he was still relatively unknown in the west. One day in 2001 Sigg dropped in to our Basel offices with Ai in tow. We went out and had a very good time together.

After that we all decided to travel to China together. Both Pierre [de Meuron] and I got on with Ai well, he has a wonderful sense of humour and is great company.

Ai is incredibly knowledgeable about the culture of old China – about everything from vases to cities – and this knowledge is reflected in his work, constantly drawing on history and tradition. But at the same time his art is very contemporary and I think this is why we made a good match. In both his work and ours you can glimpse the classical but also the radically contemporary.

We decided we should collaborate and in fact we've done many projects together but the Beijing national stadium for the 2008 summer Olympics [for which Ai was artistic consultant] is the only one to have materialised.

I feel Ai is a great architect on his own terms. He has a real talent for it. You can see that from his own architectural projects – his studio in Beijing is a wonderful building which only he could have done.

Ai loves China, and it is this affection which drives him to criticise the government. People often get that wrong. His criticism stems from his anger at the restrictions. He loves the Bird's Nest. His refusal to attend the opening ceremony was misinterpreted as a protest against the building but it was a gesture made out of political rather than artistic convictions. He uses criticism as art, he has a hugely popular and outspoken blog. Despite his criticisms, the Chinese state has unofficially recognised his importance.

Who would have thought China was ready for this kind of criticism or for our designs? We designed the stadium together as a kind of test – to see if this radical contemporary work would be embraced by China. It was, we never had any interference from the authorities.

Ai's involvement was crucial to us, not just because of his artistic vision but also because of his cultural knowledge of China. His input was also invaluable from a practical point of view; to do a project like the Bird's Nest you need strong alliances and he helped us operate in China.

He's a great artist and his work has evolved hugely over the years. He still retains a sense of tradition and craftsman-like skill. But at the same time, he is incredibly modern. I am very pleased his work will be installed in the Turbine Hall – it's the perfect setting to display his talents.