A tour-de-force of borrowed movie footage … The Clock, Christian Marclay

Photograph: Matt Greenwood/© Tate

The best art of the 21st century | Art and design | The Guardian

Steve McQueen in bed, Ai Weiwei in trouble, Pussy Riot in church and Ragnar Kjartansson in the bath – they’re all included in our countdown of the best art since 2000