Melvyn Bragg considers the 150-year history of the Two Cultures debate. In 1959 the novelist C.P. Snow delivered a lecture in Cambridge suggesting that intellectual life had become divided into two separate cultures: the sciences and the humanities. The lecture is still celebrated for the furore it provoked - but Snow was returning to a battleground almost a century old. Melvyn Bragg visits the old Cavendish Laboratory in Cambridge, scene of many of modern science's greatest triumphs, to put the Two Cultures debate in its historical context - and Paul Nurse, President of the Royal Society, reveals the influence the Two Cultures debate had on his development as a scientist. Producer: Thomas Morris.