Director of the world's most popular modern art gallery, Lars Nittve, has surprised the art world by announcing his departure from the Tate Modern. He has been offered a post as director of Sweden's national museum of art, Stockholm's Moderna Museet. Nittve has played down suggestions that this is anything to do with tension between himself and Sir Nicholas Serota, who presides over the four Tate galleries. He says: this is a once in a lifetime opportunity to direct the national museum of modern art in my own country.