In the immediate aftermath of the Easter Rising, the defeated rebels were gathered in the gardens of the Rotunda Hospital. Some 250 of them were cramped together in a tight space, exhausted and hungry after six days of fighting.
They were inspected by Capt Percival Lea-Wilson, an English-born first World War veteran who was posted to Ireland in 1916.
Lea-Wilson was an early casualty of shell-shock and was dispatched to Ireland out of harm’s way, or so it was presumed.
According to several eyewitnesses, Lea-Wilson humiliated and mistreated many of the prisoners.
He refused to allow several injured men to be taken away. Neither would he allow the men to urinate standing up so they had to do it lying down.
More egregiously he is alleged to have had Tom Clarke, the oldest of the signatories of the Proclamation, stripped and humiliated on the steps of the hospital.
"At one period I noticed Michael Collins protesting vigorously to the British officers at the maltreatment of Tom Clarke. The conduct of many of the British officers during the night can only be described as savage. In particular, Captain Lea-Wilson was brutal," recalled Capt Frank Henderson, who was an eyewitness to events.
Another eyewitness was Liam Tobin, who would go on to become the IRA's deputy director of intelligence. He remembered Lea-Wilson taunting the prisoners as being "worse than the Boche" and called a stricken prisoner a "bastard", a particularly egregious insult in the context of the time. Tobin, then 21, claimed later that he made a mental note and "registered a vow to deal with him (Lea-Wilson) at a later date".
Michael Collins considered the assassination of Lea-Wilson as a priority not just because of his actions during Easter week in 1916 but because of the assiduous manner in which he went about targeting the IRA in Co Wexford.
Ten men were detailed with the task; five on surveillance and the other five to carrying out the killing. Tobin and Frank Thornton, a member of Collins's squad, were dispatched by Collins from Dublin to ensure the killing was carried out.
Lea-Wilson had a morning routine in which he walked to the train station at Gorey to meet the 9.35am from Dublin which contained his mail bag. He bought a newspaper and walked the short distance home to his house accompanied by a RIC constable.
On successive mornings, Lea-Wilson did not turn up at the appointed time. He had, according to Sean Whelan, a local IRA volunteer, a "hangover".
On the third day, June 15th, 1920, Lea-Wilson resumed his routine.
Having parted company with a constable who was guarding him,
Lea-Wilson walked past a broken-down car which was being repaired on the side of the road. The car was a ruse. The men tending to it were his assassins.
He was perusing a copy of the newspaper – the Irish Independent, as it turned out – when Whelan, Tobin and Thornton shot Lea-Wilson at least a dozen times, including once when he was prostrate on the grounds.
Collins is said to have responded exultantly to the shooting, exclaiming to friends at the Wicklow Hotel on Wicklow Street in Dublin that night: "We finally got the bastard."
The killing is best remembered now for its association with the Michelangelo Caravaggio painting The Taking of Christ, one of the great glories of the National Gallery of Ireland collection.
Lea-Wilson left a widow, Marie Lea-Wilson, from a middle-class Catholic family in Charleville, Co Cork.
Four years after his assassination, she bought a painting at auction in Glasgow as a source of comfort, believing it was the work of a minor Dutch artist called Gerrit van Honthorst.
The price she paid for the painting is unknown, but it cost her £20 to get a new frame for it.
As a mature student, Marie Lea-Wilson later graduated as a doctor from Trinity College Dublin and practised as a paediatrician in Dublin.
She never recovered from his husband’s death and sought solace through the Lesson Street Jesuits’ community. In gratitude for their spiritual support, she gave the painting to the order in the 1930s for safekeeping.
The Taking of Christ hung in the Jesuits’ dining room in Leeson Street for decades. It had become so commonplace that the priests there failed to even notice it anymore.
Dr Lea-Wilson lived until the age of 84 and died in 1971. It was another 19 years before Sergio Benedetti, the conservator of the National Gallery of Ireland made a visit to 35 Leeson Street, the Jesuit community house, to view its art collection for the purposes of evaluation.
His identification of Caravaggio’s lost masterpiece was one of the most startling moments in the history of Irish art.
Three years later his hunch was confirmed and it went on display in the National Gallery on permanent loan. It remains one of the greatest artistic gifts ever given to the State –its value accentuated by the extraordinary chain of circumstances which led from the bloody streets of Gorey to the walls of the National Gallery.