On January 30, 1972, British soldiers murdered thirteen civilians who were taking part in a civil rights march in Derry in the North of Ireland. Another man wounded by their bullets later died. The massacre happened in broad daylight, with hundreds of eyewitnesses, including members of the international press. There was also film footage of the day’s events.

In the aftermath, there should have been no question about what had taken place in Derry. The only questions to be determined were how and why. Had the soldiers of the Parachute Regiment’s (“Paras”) First Battalion simply run amok? Or was the massacre the predictable outcome of a criminally reckless plan devised by senior officers?

Instead, the families of the victims had to wait nearly four decades for Lord Mark Saville to acknowledge that all those killed were unarmed civilians, and for the British prime minister David Cameron to apologize for their deaths. Throughout that period, the official line of the British state, as expressed in the report published by Lord John Widgery in April 1972, was that the soldiers had only begun shooting after coming under sustained fire, and that they sincerely believed their targets to be armed gunmen.