Alastair Sooke takes us on an exclusive personal tour of the Roy Lichtenstein Retrospective at Tate Modern. Offering an in-depth look at one of the year's most talked about exhibitions, Alastair and guests explore the enduring appeal of Lichtenstein's imagery, debate the controversies around his work and his influence on today's generation of artists and tackle the big question - was Lichtenstein a Pop Art genius and one of the defining image-makers of the 20th century, or a one-trick wonder whose big idea was so powerful he could never let it go?