The British Army warned any "hostile" aircraft would be met with fire following the attempted bombing of a RUC station in an operation led by an English heiress, reports from the period reveal.
Rose Dugdale, the subject of a new three-part RTÉ documentary, was involved in the operation with her partner, Donegal IRA man Eddie Gallagher.
The pair hijacked a helicopter in Donegal and dropped two milk churns packed with explosives on the Tyrone town. Neither bomb exploded.
Dugdale, now 82 and living in Cork, the daughter of a millionaire Lloyd's of London insurance underwriter, became involved with the Provisional IRA after meeting Gallagher in London.
The Strabane attack happened just weeks after moving to Ireland in late 1973. She was also involved in the Russborough House art heist in April 1974, with paintings stolen worth more than £100m in today's money.
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She was quickly caught and sentenced to nine years in prison, where she gave birth to a son by Gallagher.
Former Conservative MP Edwina Currie attended Oxford University at the same time as Dugdale, a former debutante paraded in front of Queen Elizabeth and Prince Philip aged 17 in 1958.
While Dugdale was influenced by Marxist ideology her sister Caroline married Patrick Ground, a Conservative MP in the 1980s and early 90s.
"Rose and I both took our politics very seriously," Ms Currie tells the film makers of The Heiress and The Heist. "We cared about a lot. Politically, she was an Irish revolutionary at that time, enormously sympathetic to the Catholic cause."
Dugdale and Gallagher planned the Strabane attack in January, 1974. The couple met the helicopter pilot in an hotel and he is persuaded they work for a French magazine.
When in the air, Gallagher produces a gun, places it to the pilot's head and tells him to land in the field. Others are waiting with four milk churns loaded with explosives.
Historian Diarmaid Ferriter said: "And the idea was that the helicopter would transport the 410 gallon milk churns, which would then be dropped over the RUC station.
"But the problem was the helicopter could not sustain the weight of those four milk churns.
"Two of them had to be discarded into the water before they even got near their intended target. There were two remaining. One of those turns was dropped way off target. The other was close to target but didn't detonate."
According to reports from the time, one landed about 50 yards from the police station and the other splashed into the Mourne River, about 500 yards away.
The helicopter made a preliminary pass over the police station, then circled and made the bombing run, it was reported.
In a statement, the British Army statement said “any hostile aircraft or helicopter will, in future, be engaged with fire".
The Heiress and The Heist - RTE One - Episode One - Tuesday 9:35pm
