Justice must be done for the sake of our society, for healing the memory of our terrible past and, most importantly, to bring some closure to the families of the victims.

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The message came early on a Wednesday morning. It was from Howard Varney, a lawyer representing the families of the Cradock Four. "Would you possibly be available to come to PE this Friday?"

It was a long-awaited summons. He had asked me to testify on behalf of the families more than a year ago, but there had been various delays, until, finally, came the opportunity to bear witness to the little, but significant piece of the hidden secrets I had uncovered of those terrible, violent murders 40 years ago.

On 27 June 1985, four anti-apartheid activists, Matthew Goniwe, Sparrow Mkonto, Sicelo Mhlauli and Fort Calata were returning from Port Elizabeth (Gqeberha) when their car was stopped at a roadblock.

The four were taken into the nearby bush, brutally assaulted with steel pipes and knives, shot and killed. The bodies and the car were doused in petrol and set alight.

It was one of the worst murders by apartheid police hit squads, and two previous inquests, in 1987 and 1993, found no specific individuals to be guilty of the murders, although the second inquest did find that these murders...