Lauren Laverne meets fashion designer Matthew Williamson ahead of his upcoming exhibition at the Design Museum, and Andrew Graham-Dixon visits the Tuscan city of Siena to assess its role in the Renaissance. In Reykjavik, Verity Sharp talks to Icelandic band Sigur Ros about their film Heima, which focuses on the group's series of unannounced gigs performed across their home country in 2006. Elsewhere, Tom Dyckhoff profiles some of Britain's best young architects and Mark Kermode reviews the week's movie releases.