Butter fingers… When Ai Weiwei smashed this Han dynasty urn on camera, the photographs became more valuable than the urn was in the first place. It was a defiant act of cultural recycling – out with the old and in with the new. Weiwei’s provocative works got him placed under house arrest by the Chinese government in 2011. 140,000 people petitioned for his release, Tate Modern painted “Release Ai Weiwei” on its exterior and Anish Kapoor cancelled his Beijing exhibition in a gesture of solidarity.