The ground is laid for the next revolution

Later this month, Tate Modern will open its new extension, a 260m brick-clad ziggurat designed by Herzog & de Meuron, who converted Bankside Power Station into the original Tate Modern in 2000. It prompted The Art Newspaper to consider the Tates seismic effect on the art scene in London and indeed internationally. In this special report we focus on what happened to art-making; on the Tates collecting policies; on other museums around the world and historic art; on Londons commercial gallery