When the British prime minister, Mr Harold Wilson, met his cabinet on February 26th, 1969, Northern Ireland was already high on the agenda. Violence in the North, following the People's Democracy march from Belfast to Burntollet, was a source of great anxiety to Mr Wilson and his home secretary, Mr James Callaghan.
At that meeting Mr Callaghan suggested to his cabinet colleagues that direct rule was a serious option, but independence for the North "might be a preferable alternative" in the event of a breakdown of law and order.
In the atmosphere of a gathering political storm in Northern Ireland, senior advisers to Wilson considered a series of reforming options, ranging from direct rule to independence as political and social agitation increased because of the slow pace of Stormont reforms.
However, Mr Wilson was told that unless he was willing to see the North lapse into civil war, or be absorbed into the Republic, or both, independence was not a genuine alternative.
Similarly, Mr Wilson's advisers warned against a type of "round-table conference", including all the political parties at Westminster, chaired by someone of "unchallengeable impartiality", such as the Duke of Edinburgh.
A royal presence might make it more difficult for Maj James Chichester-Clark [who succeeded his cousin, Capt Terence O'Neill, in April 1969 as the North's prime minister] to refuse such a conference to discuss the North's future, but it was eventually considered that the risk of failure was perhaps too great to engage Prince Phillip in such an undertaking.
It was pointed out that if rioting continued and lives were lost in the North, public opinion would not allow London to stand by and watch. On the other hand, the advisers told Wilson's government that it could not allow British troops to be used, in effect, to maintain an Orange faction in power and London would eventually be compelled to assume direct responsibility for reform.
The expulsion of Northern Ireland from the United Kingdom was also considered, but this option would not, it was argued, enable the withdrawal of British troops since such a move would provoke further rioting, possibly civil war, and the eventual intervention of the Republic. Furthermore, associated status for the North, provided there was sufficient agreement for it, would leave Wilson's government responsible for defence and external relations.
This scenario, he was advised, would again compel Mr Wilson to defend the North against possible intervention by the Republic, which might be encouraged to step in by civil unrest on the streets of Derry and Belfast.
Two confidential memos prepared for Mr Wilson on April 29th - just days before he pressed Capt O'Neill to accept universal suffrage in local elections in the North - reveal the extent to which the problems in the North perplexed officials in London.
"If we withdrew, the regime would be likely to become more illiberal or no regime capable of maintaining law or order would exist," Mr Wilson was told.
"In that situation we should be under strong political pressure to intervene and, whether we refused or not, there seems a strong likelihood that political pressure would compel the Irish Republic to step in and annexe the Six Counties," the second memo suggested.
Mr Wilson's cabinet was clearly prepared for the possibility of civil war or serious anarchy in the North and Mr Wilson already had a "war book" in an advanced stage of preparation which had a range of options that could be implemented in the event of a crisis in Northern Ireland.
The defence secretary, Mr Denis Healey, had told the cabinet on February 19th that no British army units would be used in the North that had a preponderance of Irishmen; direct rule had been worked out in detail and a governor would be appointed to take control in the North. By August, Stormont was losing its grip on law and order and the civil rights movement, encouraged by the newly elected MP for Mid-Ulster, Ms Bernadette Devlin, was gathering momentum. At a meeting in London on August 1st, Dr Hillery informed the British foreign secretary, Mr Michael Stewart, that if trouble spilt over into the Republic, Dublin could no longer consider the North as a purely British problem.
Mr Wilson was on holiday in the West Country when violence erupted on the Bogside after the Apprentice Boys march in Derry on August 12th. Mr Wilson had originally favoured banning the march but was persuaded to allow it on the grounds that such a decision, pressed on Stormont by Westminster, might provoke the Protestant backlash that would sweep Chichester-Clark's regime from power, causing chaos on the streets.
The next day, the RUC used CS gas for the first time against Catholic rioters; it was the first time it had been used by police in the United Kingdom.
Then on August 14th, with the law and order deteriorating in Derry and Belfast, as Catholic was pitched against Protestant, Mr Wilson flew by helicopter to Culdrose, near Penzance, for a crisis meeting with Callaghan and the GOC in Northern Ireland, Gen Ian Freeland.
Cabinet papers reveal that Mr Wilson and Mr Callaghan agreed that if Stormont sent a request to send in British troops it could be met immediately, since the cabinet had already given its agreement to the move before the parliamentary recess in the summer. Five minutes later, when Mr Callaghan was airborne on his return to London, the request from Stormont was received and the order was immediately given.
Mr Wilson met Maj Chichester-Clark in London a week later, ahead of the publication of the Downing Street Declaration, a seven-point plan committing Stormont to implementing equal rights and protection under the law for all citizens.
Mr Healey pointed out there were already signs that the honeymoon period for British troops in the North was ending and the foreign secretary warned Mr Wilson that Dr Hillery intended to raise the North at a meeting of the UN Security Council.
A week after Mr Wilson met Maj Chichester-Clark, Mr Callaghan visited Belfast and Derry and tried to meet political leaders from both communities and members of the civil rights movement, as well as the Stormont politicians, whom he found, he commented later, "bewildered and inert".
Reporting back to the cabinet on September 4th, Mr Callaghan told his colleagues that although it had been difficult to arouse Stormont to the full gravity of the situation in Derry and Belfast, Maj Chichester-Clark and his ministers would be ready to co-operate once Westminster had given the lead.
Mr Callaghan was worried about the danger of a Protestant backlash in which the Unionist Party would lose support, not to the left but to the right, if political and social reform and the question of the B-Specials were not handled carefully.
Disarming the B-Specials would be difficult. Mr Callaghan confidently predicted that the commandants would obey orders to disarm, but there was some doubt over whether all their men would follow them. Handing in their arms was "extremely delicate" since there were reports that arms had been finding their way to Protestant volunteers "controlled" by the Rev Ian Paisley.
As Dublin witnessed the reality of British troops on the streets of Derry and Belfast, Mr Callaghan was sufficiently alarmed a few days later to inform the cabinet that Mr Jack Lynch's attitude was not helpful or easy to assess.
Mr Lynch had sent Irish soldiers to the Border but had renounced the use of violence. Mr Callaghan informed his colleagues that if Mr Lynch wanted a united Ireland, he must conciliate Protestant opinion, but so far his tactics had done nothing but alarm it. As things stood, Mr Callaghan said, efforts to lift Anglo-Irish relations to a higher plane would take a long time.
The publication of Lord Hunt's report on reform of the RUC in October - it recommended that the force be stripped of its paramilitary role and the disbandment of the B-Specials - was universally endorsed by Mr Wilson's government but violently condemned by a group of loyalists in Belfast.
During the ensuing violence, when the group clashed with the RUC, Constable Victor Arbuckle was the first RUC officer to be killed in the Troubles.
As the year drew to a close, Mr Wilson was increasingly sensitive to Chichester-Clark's difficulties, and although he did not want to assume direct rule, the plans were already in place for London to take control in case Stormont fell. Force might be necessary as a last resort.
"The use of force would have the gravest implications," he told his cabinet in September 1969, "and the GOC Northern Ireland has expressed strong misgivings about the consequences of our becoming involved, as we well might be, in an urban guerrilla war."
Rachel Donnelly is an Irish Times journalist