In 1961, the United Nations (UN) secretary-general Dag Hammarskjöld was among 16 people killed when his plane crashed in Zambia, or what was then Northern Rhodesia.
He'd been en route to broker talks to end the civil war in neighbouring Congo.
The 58-year old mystery of why the plane went down is still under investigation, with many believing the South African apartheid government was involved.
Last December, a UN investigator looking into new evidence, criticised the UK and South Africa for their lack of cooperation.
Meanwhile, a new documentary has been released probing the apartheid regime's reported involvement in Hammarskjöld's death.
It also makes startling claims about a South African organisation allegedly involved in a global plot to spread Aids on the continent.
On Weekend Breakfast, Phemelo Motene speaks to Andreas Rocksén, producer and head of research, .
Rocksén says after many diplomatic successes during the Cold War era, Hammarskjöld was perceived as a threat by governments and organisations with vested interests on the African continent because of his support for the independence campaigns of a number of countries.
His engagement for the newly liberated countries also became a threat to the superpowers that had interests in Africa and elsewhere... In many places assets were nationalised... Money was lost...— Andreas Rocksén, Producer and head of research - Cold Case Hammarskjöld
Phemelo quizzed Rocksén about proof of South Africa's alleged involvement in a plot to kill the UN chief.
In 1998 there were documents surfacing in South Africa in the Truth and Reconciliation Commission's work where an organisation called the South African Institute for Maritime Research, they claimed... a plot to kill him.— Andreas Rocksén, Producer and head of research - Cold Case Hammarskjöld
As I understand, the TRC did not have the mandate to work with cases outside of South Africa... It also surfaced at the end of the time of Desmond Tutu at the commission.— Andreas Rocksén, Producer and head of research - Cold Case Hammarskjöld
That's why he presented it to the press, saying ok we have these documents... It was up to media and others to investigate further, but nothing happened.— Andreas Rocksén, Producer and head of research - Cold Case Hammarskjöld
No one took that further, there were no journalists in SA who tried to understand more or dig deeper in the case. That is what we have done. We have managed to establish the existence of this organisation and have found supporting documents.— Andreas Rocksén, Producer and head of research - Cold Case Hammarskjöld
According to Rocksén, there is also evidence that the paramilitary South African Institute for Maritime Research aimed to spread AIDS to try and maintain white supremacy in the region.
He says South African officials have been uncooperative about investigating further.
We have tried to reach out but we have not got any response.— Andreas Rocksén, Producer and head of research - Cold Case Hammarskjöld
The UN itself however, is continuing its investigation.
They are actively investigating - not the case of Aids being spread but the case of Dag Hammarskjöld... I think there is a report expected in the summer.— Andreas Rocksén, Producer and head of research - Cold Case Hammarskjöld
'Cold Case Hammarskjöld' is being screened during the Encounters Documentary Film Festival running from 6-16 June in Johannesburg and Cape Town.
Headline pic from Encounters Facebook page
For more of the gripping interview with the producer, take a listen: