No organisation claimed responsibility for blowing up Aghalane Bridge in November 1972 but it was widely believed to have been the work of loyalist terrorists.
Whoever detonated the bomb precipitated the closure of the main Enniskillen to Dublin road just south of Derrylin and severed the links between communities in Fermanagh and Cavan.
They also ignited a political row between unionists and nationalists over whether or not it should be re-opened, Government papers released after 30 years reveal.
According to the documents held in the Public Records Office in Belfast the British security forces did not want the bridge rebuilt.
At the time Fermanagh was being ravaged by bloodshed and violence. In the weeks prior to the bridge being blown up members of the UDR and IRA engaged in a gun battle near Newtownbutler, a shop was destroyed in an explosion at Tullyhommon, a 700 pound bomb was defused in Rosslea and soldiers were injured in a blast at Oakfield, Magharveely. Around that time 5,000 people attended the funeral of Reserve Constable Joseph Calvin, from Derrin Road, Enniskillen, killed when a bomb went off under his car in the town's Quay Lane Car Park. Another police officer, Constable Robert Keys, a father of six from Bannaghmore, between Kesh and Pettigo, died in a rocket attack on Belleek Police Station.
In the midst of the violence Aghalane Bridge was blown up, prompting a letter from the local nationalist MP, John Carron, to Lord Windlesham, Minister of State at the Northern Ireland Office, calling for it to be re-opened.
Mr. Carron said the cross-border bridge served the whole western side of Northern Ireland and its closure would hit "the only source of employment in the area, mainly local sand and gravel companies which traded with the Republic".
In a note for the Minister on December 12, 1972, a Government official referred to the "political aspect" of the issue.
"The protestant community of this area are in constant fear of raiders from across the Border," he said.
"They have already suffered loss of life and damage to property," he added.
"Irrespective of who destroyed the bridge, � they will view its restoration with suspicion," the official stated.
The issue was raised by Lord Kilbracken, an Irish peer in the House of Lords and the road was re-opened when a temporary bridge was erected from the County Cavan side.
However, in December 1972 a bomb exploded in nearby Belturbet in County Cavan, killing two teenagers, Geraldine O'Reilly and Patrick Stanley.
Captain John Brooke, unionist Chief Whip and Chairman of Fermanagh County Council blamed Lord Kilbracken and Cavan County Council for the deaths.
He alleged that they had "re-opened the bridge", thereby giving "easy access for terrorists".
On December 27, 1972, Lieutenant-Colonel A. T. P. Millen noted that "the destruction" of Aghalane Bridge "suits us well in that it closes a route frequently used by Republic-based terrorists".
The temporary bridge was subsequently blown up, closing the main Enniskillen to Dublin road for over a quarter of a century.
It was not until 1999 that a new bridge across the Woodford River re-opened the route.