In 2008, an earthquake in China’s Sichuan province killed almost 90,000 people. Many were crushed when school buildings collapsed, exposing their poor construction quality.

To counter perceived government suppression of information, the artist Ai Weiwei made an artwork from 90 tonnes of steel bars salvaged from the schools' wreckage.

In 2011, Ai Weiwei was detained in harsh conditions for 81 days and banned from leaving China. While his official charge was tax evasion, his detention was widely viewed as a response to his activism. But the artwork, Straight, became a global sensation. Ai Weiwei tells the story to Ben Henderson.

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(Photo: Ai Weiwei in front of his artwork, Straight. Credit: Leon Neal/AFP via Getty Images)