How Ai Weiwei’s years living in an underground hole haunt his art to this day

 Ai Weiwei is one of the most famous artists in the world, but infamous to the Chinese authorities. To them he is an outspoken, critical troublemaker.

Eight years ago, after a period of imprisonment and then house arrest in Shanghai, he left China and now lives in Portugal, but his work is always about China and often using ordinary objects and found materials to comment on his country's past and present.