The artistic director of Serpentine, recalls 35 years of friendship and collaboration with the cultural impresario who was one of the most important curators of the second half of the 20th century

The former director of Cologne’s Museum Ludwig “shaped the art discourse of the last five decades like no other", the museum says

In a unanimous decision, the government’s advisory commission says it is likely the work was sold under duress

Influential works by Duchamp, Picasso and Mondrian also celebrate centenary this year