Has any generation in history ever banged on about itself more and with less merit than the baby boomers? Oh good, another 1960s retrospective. And another. And another. You can't move for celebrations of "the decade that changed the world forever". Tate Britain is honouring the art of the swinging decade in an exhibition starting at the end of the month. BBC Four is a week into its Summer in the Sixties season, while the Sunday Times magazine is devoting acres to the 10 years that shook the planet. Why this surge of interest? Has a milestone passed? Or is...