Two South African men. Both white. Each played a significant role in upholding apartheid. Each intimately involved in killing other human beings in support of white supremacy. One I knew. One I didn’t.

Craig Williamson was a high-ranking officer of the much-feared Bureau of State Security (“Boss”). In 1977, in the guise of an anti-apartheid activist, he led me across the border from South Africa to Botswana when I escaped from house arrest. He then became one of the most successful double agents in history and badly undermined the assassinated Swedish prime minister Olof Palme’s efforts to assist anti-apartheid activity.

In 1980, after Williamson had been unmasked as an apartheid spy, he returned home a hero and went on to even higher office in South Africa as a member of the State President’s Council. He was also the hands-on architect of the killing by parcel bomb of two people I knew. Two heroes of the apartheid struggle. Both white. Both women.

One, a best friend, Jeanette Schoon (and her six-year-old daughter), splattered against the walls of their home in exile in Angola. The other, Ruth First, blown up in Mozambique. There were many others whose blood is on his hands who I didn’t know.

Williamson went before the Truth and Reconciliation Commission (TRC) in 2000 and confessed to his role in these killings but little else, claiming that they were “legitimate acts of war”. He offered no remorse. He offered no information that could ease the pain of those whose loved ones he’d killed. He received a full amnesty and resumed a normal life in South Africa as a security consultant. In his case, the TRC achieved neither truth nor justice for the victims and their families.

The other man is Eugene de Kock, alias “Prime Evil”, who was the head of the apartheid regime’s death squad, which tortured and killed opponents with impunity. In 1996 he was sentenced to 212 years in jail for crimes against humanity. He went before the TRC, said he was truly sorry and offered comprehensive information on his victims to the families, how they died and where they were buried. He was granted amnesty for some crimes but his prison sentence stood. He was set to rot in prison for ever.

The two men are connected. In 1996 de Kock testified that Williamson had been involved in the assassination of Olof Palme. In his testimony, de Kock said that the murder, by a lone gunman who shot Palme in the back of the head, had been the work of Operation Long Reach – a secret apartheid-era programme, set up to harass, silence and gather information about opponents of the South African government abroad.

Ten years ago Professor Pumla Gobodo-Madikizela, a psychologist, wrote a book about the encounters she had with de Kock when, at the personal invitation of Nelson Mandela, she served on the TRC. Their meetings happened in the maximum-security section of Pretoria Central Prison. She is elegant, highly intelligent and black. He a baby-faced white killer. He in orange prison overalls, feet chained. She seated in a chair with wheels so she could scoot out of danger should the need arise. Her subject is the nature and origins of evil, the power forgiveness bestows on the victims and their relatives and the conditions for perpetrators’ readmission to the human community. It serves no former repressive society well to ring-fence evil in a few individuals and absolve the rest. The capacity for evil and good resides in us all.

Gobodo-Madikizela firmly believes that de Kock should be pardoned and allowed back into society. He accepts full responsibility for what he did and has asked forgiveness from his victims’ families. De Kock is the only apartheid police official still imprisoned and his latest application for parole is pending. None of his colleagues or superiors was imprisoned.

I read Gobodo-Madikizela’s book, A Human Being Died That Night, and optioned the rights to produce a play. Shortly afterwards, her 40 hours of taped interviews with de Kock were stolen from her assistant on a Cape Town train while en route to make copies for me. The professor was understandably distraught. I arranged for a reward for their return to be offered through radio announcements and posters at railway stations.

If the tapes had been taken by South African intelligence agents or ex-agents we stood no chance of getting them back. But the reward would be attractive to a petty criminal. Three months later Professor Madikizela received a telephone call. A priest in a black township said a local gangster had some audiotapes. Victory? Kind of. He had only four tapes out of 40.

I commissioned the South African-born Nicholas Wright to write a play based on her book and the remaining tapes. When the production opened at the Fugard Theatre in Cape Town in February (it’s now running in London at the Hampstead Theatre Downstairs until 21 June) the reaction was profound. Most black people who saw it felt de Kock should be released: Archbishop Tutu voiced the same opinion. White viewers were less certain.

The play deals with horrific officially sanctioned apartheid-era murders and the physical and emotional pain of victims and survivors, but it is bathed in the overwhelming humanity and intelligence of the black character, Pumla Gobodo-Madikizela.

Eric Abraham was a foreign correspondent in South Africa in the mid-1970s

Pumla Gobodo-Madikizela’s “A Human Being Died That Night” is published by Portobello Books (£3.99)

ARTICLE IN THE NEW STATESMAN