Cold Case Hammarskjöld

In 1961, Secretary General of the UN, Dag Hammarskjöld, died in a plane crash in Northern Rhodesia. He was en route to ceasefire negotiations between non-combatant UN forces and troops from the breakaway state of Katanga. The circumstances of the plane crash were always unclear but now the UN are reopening the case on the suspicion of assassination. The question is, who wanted Hammarskjöld dead and can the truth be revealed today?