The documentary marked the 30th anniversary of the assassination of Lord Louis Mountbatten by the Provisional IRA. Mountbatten was Prince Philip's cousin, the last Viceroy of India and Prince Charles's mentor. He was also a lover of Ireland. He holidayed at his home in the seaside village of Mullaghmore each summer.
On 27 August, 1979, Mountbatten, his family and a local teenager, Paul Maxwell, who he had hired as a deck hand, went lobster-potting in his boat.
An IRA member, Thomas McMahon, had slipped onto the boat the previous night and attached a radio-controlled bomb. When the boat was en route to Donegal Bay, McMahon detonated the bomb from shore. The blast killed Mountbatten, his elder daughter's son and Maxwell.
The aftershocks were immense. The event rocked the sleepy fishing village, provoked an already delicate political situation and devastated families from both sides of the divide.
In part, the documentary examined the story of an aggrieved father and his journey from rage and retribution to peace and reconciliation.
John Maxwell described the day with heart-rending candour, recalling how he reacted to his son's dead body when it had been retrieved from the water.
"Paul was lying there and his head was in a bucket of mackerel... I lifted him up and his body was still warm."
They also managed to get the Former IRA chief of staff, Ruairi O Bradaigh, to admit that he vetoed an earlier plot to "get Mountbatten" from a unit in west Fermanagh.
More revelatory was O Bradaigh's reaction when the programme-makers told him that they had uncovered evidence to suggest that Mountbatten was favourable towards the reunification of Ireland.
"I didn't know that," he said. "He should have spoken up ... Who knows, it could have changed the course of history."
Mountbatten did change the course of Irish history, but he didn't live to see it. His death spearheaded talks between the two governments.
Jack Lynch had a tense meeting at Downing Street, at which Thatcher almost "leapt over the table" in anger when it was suggested there was "sympathy" in [the IRA's] aims. "Murder is murder is murder," she yelled.
It's just one example of the many vignettes the programme-makers collected. The angles explored and anecdotes uncovered gave extra depth to an already powerful story.
A little more on the notorious vanities of Mountbatten would have been appreciated. He famously organised his own televised funeral, for instance.
Nor did they explore his personal reasons for the curious lack of security.
Even so, the tireless research, unusually forthcoming contributors and tight editing made this a compelling piece of television.
Mountbatten: Return to Mullaghmore * * * *