There were accounts of routine and bizarre acts of torture beatings with barbed wire, bicycle chains and iron bars.
His prominence in the darkest days of the exiled ANC seems to have been overlooked, says David Beresford.
The long-running drama over Jacob Zuma and the arms deal has resulted in the country overlooking an aspect of the ANC president's background which says even more about his fitness, or otherwise, to govern.
At the end of last year, a biography was published on Zuma which was perhaps more interesting for what it did not contain. Written by journalist Jeremy Gordin, it fails to mention, for instance, that Zuma was a life-long communist.
Zuma seems to have been anxious not to have this detail widely known. Nor is membership of the SA Communist Party mentioned in Zuma's government and ANC biographies.
Curiously, however, it is mentioned in his autobiography.
A favourite technique of identifying enemy agents in the ANC was to make members endlessly write their life stories.
The theory was that an enemy agent trying to stick to his or her cover story would sooner or later make a blunder which would be pounced on by their interrogator.
On May 2 1985, Jacob Zuma, alias "Pedro", sat down to write his story. The Zuma autobiography published by the radical investigative magazine, Molotov Cocktail says he joined the SACP (or 'the family' as it is euphemistically referred to) at the age of 21, in 1963.
Zuma's autobiography also mentions his membership of "NAT" the dreaded security department of the ANC in exile. Popularly known as the "Mbokodo" "the stone that crushes" NAT was a department of the ANC, but seems to have taken on a life of its own.
Set up in 1969, NAT was answerable to the Revolutionary Council, which in turn fell under Oliver Tambo at the office of the ANC president.
In the '80s NAT concentrated on disciplinary functions and guard duties in places such as Quadro (the ANC's main detention camp in Angola, sometimes known as Quatro), moving away from intelligence activities.
In 1987 Joe Nhlanhla was appointed director of the Mbokodo with Zuma his deputy.
A senior intelligence official testified to one inquiry that the "powers" of the Mbokodo were "pervasive". They did not consider themselves accountable "to the ANC generally or answerable to anybody specifically, other than its head".
The nature of Mbokodo can be best conveyed by an account of some of the allegations arising from the 1983 Quadro mutiny.
There have been three internal inquiries by the ANC into the camps scandal, and the horror stories that emerged are beyond dispute.
There were accounts of routine and bizarre acts of torture beatings with barbed wire, bicycle chains and iron bars and food and water deprivation.
Detainees were made to crawl through colonies of red ants with pig fat rubbed into their skin. A prisoner had his lips burned by cigarettes and his testicles squeezed with pliers; a detainee was buried up to his neck before being suffocated with a plastic bag; a woman had a guard masturbate over her because she refused to have sex with security officials. A trainee tried to commit suicide after his girlfriend was "taken away". People were locked up in goods containers, in suffocating conditions. And people simply disappeared.
According to the Motsuenyane Commission report the most comprehensive of the inquiries there were also "rumours of rampant embezzlement of funds, illicit dealings in precious minerals and theft of motor cars" by leaders of NAT.
Thanks to Zuma's predilection for secrecy, his part or otherwise in all this is difficult to discover. He is quoted fatuously in Gordin's book as saying details of the "operational events of those days" were the "property of the ANC, not his".
The little that is known about Zuma's "missing years" is no more than a confusion of dates to be found in government biographies and listings of commanders submitted to the Truth and Reconciliation Commission.
Two murders are central to the story of the Mbokodo. The first is that of Mzwakhe Ngwenya, better known by his nom de guerre of Thami Zulu, or TZ.
TZ was an extremely popular commander in the ANC whose death in 1989 is a cause célèbre.
Commander of the "Natal machinery", he died a few days after being released from ANC detention. He had been held by the Mbokodo for 14 months without charge, including eight weeks in solitary. Forensic evidence indicates he was poisoned.
TZ's deputy, Cyril Raymond (a.k.a. 'Edward Lawrence', a.k.a.'Ralph' a.k.a. 'Fear') was also detained. He died while in the custody of the Mbokodo, denying that he was a police spy. He apparently drowned in his own vomit.
The death of TZ caused such an uproar within the ANC that the organisation was forced to set up a commission of inquiry into it. It found no evidence that Thami was a South African agent.
The other murder is that of Benjamin Langa, which is not as well-known as TZ's killing, but could be as explosive.
Ben Langa was the brother of Chief Justice Pius Langa, and of writer Mandla Langa.
Ben was shot dead in May 1984. The killing was carried out by two gunmen Sipho Xulu and Lucky Payi both of whom were hanged for the killing.
They were helped in the murder of Ben by Joel George Martins, a friend of Ben's. Martins took the two killers to the flat where Ben was staying and called out to him, whereupon Ben opened the door to his murderers.
Martins subsequently applied to the TRC for amnesty for the killing and explained he had been told by Xulu that they had orders from a senior commander in Swaziland to kill Ben for having "sold out comrades".
The man who gave this order was code-named "Ralph", according to Martins. It was the same Ralph, or Fear, mentioned above who drowned in his own vomit while being detained by the Mbokodo.
But in another twist to this extraordinary tale, the two killers testified in their Pietermaritzburg trial that the man who gave them orders to carry out the murder was not Fear, but one "Leonard".
Jacob Zuma was also due to have testified at the hearing, but failed to turn up. A TRC amnesty panel was told arrangements had been made for him to appear, but he had gone to Geneva. George Bizos SC, who appeared for the Langa family at the hearing, said he had been unable to get a statement from Zuma.
Fear's alleged "culpability" has won wide credence, thanks to the ANC leadership. Thabo Mbeki, for example, submitted a statement to the TRC which found its way into its final report. It said: "In a few cases, deliberate misinformation resulted in attacks and assassination in which dedicated cadres lost their lives. In one of the most painful examples of this nature, a state agent with an MK name of Fear ordered two cadres to execute Ben Langa on the grounds that Langa was an agent of the regime. These cadres, Clement Payi and Lucky Xulu, carried out their orders. This action resulted in serious disruption of underground and mass democratic structures in the area and intense distress to the Langa family, which was the obvious intention of Fear's handlers.
"Once the facts were known to the leadership of the ANC, President Tambo personally met with the family to explain and apologise for this action. Xulu and Payi were arrested and executed. A triple murder had been achieved by the apartheid regime without firing a single shot."
The basis on which Mbeki was able to identify Fear as a police agent and a murderer is not known.
The peculiar thing for the Langa family is how the ANC could have "executed" Ben by mistake when he was so well known in KwaZulu-Natal and further afield. Ben's brother Mandla recalls that one of the trigger-men, Xulu, was a personal friend. Mandla had in a sense "adopted" the youngster when they were based at the ANC's Malange camp in Angola.
In fact, the friendship with Ben was even closer. Xulu testified that Ben had actually recruited him into the ANC and had helped him get out of South Africa. In exile Xulu had risen to the rank of battalion commander before being sent back to kill his sponsor and friend.
Asked by counsel when and where he was given instructions to kill Ben , Xulu said it was on the way from Mbabane in a car driven "by the regional chief of security, Umkhonto weSizwe".
"While we were in the motor car he then said to me. .. there is a person who has done us a lot of harm. I asked him: 'Who is that person?' He said the person was Ben Langa. I said: 'It cannot be Ben Langa.'" He said he went on to explain his relationship with Ben.
An exhibit in the Pietermaritzburg trial was a decrypted code book. One entry read: "Ben Langa eliminated on May 20. Reason: Leonard informed us on the day we left that Ben is the guy who handed two comrades to the Boers."
There was only one ANC cadre named Leonard in the region at the time. He flatly denies having been a "regional chief of security", or having had the conversation recounted by Xulu. His only connection with Ben was that he (Ben) had been seen with a former policeman in Wentworth and he (Leonard) had sent a report to this effect to Jacob Zuma.
Beresford is a staff correspondent of The Observer. This article is based on research for a book he is preparing on commission from Jonathan Ball publishers, with the support of the Taco Kuiper Fund for Investigative Journalism.