PREVIEW In his first film about an openly gay man, Terence Davies explores the complex and contradictory life of poet Siegfried Sassoon. Best remembered as an anti-war poet, the young Sassoon, in a marvellously understated portrayal by Jack Lowden, survives the traumas of service in World War I to enjoy an active sex life during the Roaring Twenties – love affairs with Ivor Novello and Bright Young Thing Stephen Tennant, among others – to a compromised and somewhat bitter…