An inquest into the sectarian murder of 10 Protestant workmen by the IRA in the North 40 years ago will begin today.
More than five weeks have been set aside for the coroner's inquiry into the Kingsmill massacre.
The textile factory workers were ambushed as they travelled along the Whitecross to Bessbrook road in rural south Armagh on January 5 1976 - one of the darkest years of the Troubles.
Their minibus was stopped and those on board asked their religion by the gunmen.
The only Catholic was ordered to flee as the armed men, who were hidden in the hedges, opened fire.
The 10 men who died were John Bryans, Robert Chambers, Reginald Chapman, Walter Chapman, Robert Freeburn, Joseph Lemmon, John McConville, James McWhirter, Robert Samuel Walker and Kenneth Worton.
Father-of-three Alan Black, 72, was hit multiple times but miraculously survived.
The Kingsmill attack was claimed by a little-known republican paramilitary group considered to be a front for the supposedly-on-ceasefire IRA.
However, in 2011, the Historical Enquiries Team of independent detectives found the IRA had been responsible and had targeted the workmen because of their religion.
No-one has ever been convicted.
An original inquest in 1978 lasted just 30 minutes and recorded an open verdict.
In 2013, Northern Ireland's Attorney General, John Larkin, ordered a new coroner-led probe following a long campaign for justice by Mr Black and bereaved relatives.
Victims campaigner William Frazer said: "This has been a long hard road for the families of those murdered at Kingsmills - they have waited over 40 years to see any sort of inquest into the murder of their loved ones.
"The Kingsmills massacre was a brutal sectarian attack which shocked all decent people in Northern Ireland. The sheer sectarian brutality of this attack makes it one of the most notable terrorist acts in our troubled past."