By Dominic Casciani
BBC News at the National Archives
Strike: Loyalist-led protests blockaded Northern Ireland
Ministers dismissed a strike which wrecked a 1974 power-sharing deal in Northern Ireland as the "last fling" of loyalist extremists.
The Ulster Workers' Council strike in May 1974 led to the collapse of the Sunningdale agreement.
But documents released by the National Archives, reveal how the government underestimated the threat.
Prime Minister Harold Wilson considered pulling out of Northern Ireland even though it would lead to bloodshed.
The strike came after months of ferocious political opposition from some unionists to the Sunningdale Agreement.
This deal created a power-sharing executive between unionists and nationalists and created a role for Dublin in Northern Ireland's administration.
On 15 May the Ulster Workers' Council, a loose coalition of loyalist and hardline unionist groups announced a general strike.
The strike, which lasted for two weeks, would later be enforced by blockades run by loyalist paramilitaries.
Northern Ireland Secretary Merlyn Rees telephoned Mr Wilson to tell him not to worry.
He declared the strike was the "last fling by the Protestants" and the power-sharing strategy was "closer to success than ever".
Within days, the minister's mood had darkened and he flew to Chequers for emergency talks with the prime minister.
Troops alone were not enough to break the blockades which were fast bringing Northern Ireland to a halt.
Wilson asked the minister what radical measures could be taken to smash the strike.
Could the police be used to stage something similar to Operation Motorman, the 1972 move which broke the IRA's barricades of parts of Londonderry.
"The Royal Ulster Constabulary are much more wobbly - very wobbly," said the minister.
"Well they are their people," replied the prime minister.
On 24 May Harold Wilson held an emergency Cabinet session to discuss the crisis.
He was now convinced the strike was intent on "destroying the constitution" and without firm action power-sharing would collapse.
But at the same time, officials appeared at a loss as to how to restore order.
The Army believed it could not run power stations without their managers, and nobody thought managers could be found from elsewhere.
Four days later the strike broke Sunningdale when the unionist members of the power-sharing executive quit. The Assembly was suspended and direct rule from London resumed.
Papers detailing the aftermath of the strike reveal that Wilson was accused by more than one side of having given in too readily to force.
In talks with the Irish premier, Liam Cosgrove, Mr Wilson defended his actions, saying "no army in the world however numerous could have broken a strike of that kind".
Year of violence: 1974 was one of the worst years of the Troubles
But, in a briefing on the aftermath of the strike, one official told the prime minister that Sunningdale's collapse had indeed strengthened the hand of extremists.
Setting out scenarios for a way forward, the unnamed official warned that should a majority of hardline loyalists be elected to a future assembly, they would probably directly challenge London's authority over Northern Ireland.
But if events drifted, Northern Ireland could witness a civil war leading to a redrawing of the border and mass refugee movements as communities are forcibly moved.
A document still secret, but referred to in other papers, resurrects an idea from earlier in the Troubles of a complete pull-out from Northern Ireland.
Such actions would however be an "Armageddon-type situation" with "humiliation and bloodshed" on all sides, warned an official. In time, it would suck the Irish Republic into a border war and prompt the United Nations to prevent sectarian massacres between Catholics and Protestants.
Wilson was clearly depressed by the failure of power-sharing.
He said: "It is clear that we are in the position of 'responsibility without power'."