In June 1961 the late Conor Cruise O’Brien was sent by UN Secretary-General Dag Hammarskjöld as his personal representative to the Congo’s mineral-rich province of Katanga, where Moïse Tshombe had declared secession, backed by Belgian forces and the mining companies headed by the Union Minière. Five years later I went to work for Cruise O’Brien at New York University, where he had become Albert Schweitzer Professor, and got to know this brilliant, witty, subversive Irish intellectual, whose appetite for conspiracy theory had been aroused by the Warren Report on the assassination of John F Kennedy. The American president had clearly been killed by gunfire – but by whom? According to the Warren investigation, it was done by a single assassin, Lee Harvey Oswald. Conor Cruise O’Brien, already the author of To Katanga and Back, a book rich in conspiracies brilliantly unravelled, was not to be taken in. (His surname is in fact Cruise O’Brien, although most writers, including Susan Williams, the author of Who Killed Hammarskjöld?, call him O’Brien – indeed he appears thus in Hammarskjöld’s diaries.) 

Kennedy’s violent death had been preceded two years earlier by that of Hammarskjöld himself, and it was odds-on that Conor would come up with a conspiracy theory to prove that the fatal plane crash at Ndola in September 1961 was no accident – not a case of pilot error, but