This gripping thriller, part of the BFI's Bogarde retrospective, daringly smashed through 1961's homosexual taboos, but has weathered best as a study of blackmail and paranoiaAs part of a retrospective season dedicated to that utterly unique English actor Dirk Bogarde, BFI Southbank is this week screening his 1961 film Victim. Bogarde stars as Melville Farr, a brilliant, upwardly mobile barrister with a dark past: he…