The documents have potentially global implications because they undermine the basis for a 1978 ruling by the European Court of Human Rights, which found that the so- called five techniques - hooding, stress positions, white noise, sleep deprivation and deprivation of food and water - constituted cruel, inhuman and degrading treatment but not torture.
At a recent meeting to mark the international day against torture in London, journalist Ian Cobain warned that attempts to scrutinise Britain's record in relation to torture were facing a significant backlash from the Ministry of Defence.
Cobain's Cruel Britannia: A Secret History of Torture makes it clear that it's not only the MOD that has questions to answer about interrogation in Northern Ireland. He records the role of the Whitehall Security Co-ordinator Sir Dick White, a former head of MI5 and MI6, who visited Belfast in March 1971:
For White, whose earliest experiences with MI5 had included Camp 020 and the successes of the Double Cross system, it was an axiom, reinforced by a lifetime's work, that interrogation held the solution to the growing confusion and disorder in Northern Ireland. Ministers were informed that a number of individuals were to be subjected to interrogation in depth and that they would be 'liable to be subjected to a measure of fatigue, isolation and noise'. They were not told of the precise methods to be employed.
Despite the role of its former head, MI5 has been able to obscure the full extent of its involvement in these events.
Spooks, The Unofficial History of MI5 by Thomas Hennessey and Claire Thomas, states of this period:
Wisely, when a request for assistance in the setting up of an RUC Interrogation Centre was discussed on 24 March 1971 at a meeting in the Ministry of Defence with representatives of MI5, the Security Service passed up on the opportunity to help and it was agreed that assistance should be provided by the Joint Services Intelligence Wing which was recognised as the only official school for interrogation training .
Matters are not so simple. A few paragraphs earlier, Henessey and Thomas note that "by April 1971 the army's Director of Intelligence at Headquarters Northern Ireland had established a close relationship with the Head of Special Branch (HSB)' in the RUC. They add that the Director 'was, in practice, achieving a large measure of control by these informal means' .
What they do not mention is that since 1969, the post of Director of Intelligence at HQ Northern Ireland had been filled by an MI5 officer. This salient fact was also passed over in the account of MI5's role in Northern Ireland given to the Harte Inquiry by one of the service's senior officers , and in the official history of the service by Christopher Andrew .
However the Director of Intelligence from 1970 to 1972 confirmed to the Bloody Sunday Inquiry that he was an MI5 officer when he gave evidence under the name 'David' .
The director during this period has also been named by two journalists, Simon Winchester and Nigel West, as David Eastwood, a veteran of Arnhem, where he won the MC as a paratrooper, and of the Malayan Emergency, during which he served as district commissioner in Trengganu . Eastwood's role appears to be confirmed by the appearance of his name in declassified documents, in contexts interchangeable with references to the Director of Intelligence .
The post of Director of Intelligence had been created at the outset of the Army's intervention in Northern Ireland in August 1969 . The first incumbent appears to have been Christopher Herbert, another MI5 officer with long experience of India and South-east Asia .
The earliest directives issued in 1969, suggest that the role of the director was to co-ordinate civil and military sources of intelligence . Later drafts produced during the intelligence re-organisation following direct rule in 1972, state that the director had responsibility for 'the direction of military intelligence in Northern Ireland'.
Did this reflect existing practice? If so, it raises a key question: to what extent did MI5's colonial policemen have control of those controversial army operations of the early 1970s which had an intelligence dimension? More usually associated with army officers such as Frank Kitson, these included the agent-running activities of the Military Reaction Force, and deep interrogation itself, known as Operation Calaba.
There was at least one notable contemporary allegation of MI5 involvement in interrogation, in Simon Winchester's 1974 book Northern Ireland in Crisis. According to Winchester, the first dozen subjects for interrogation in depth, were taken to Ballykinler Barracks in County Down.
At Ballykinler, the men were handed over, not to policemen or soldiers or Stormont civil servants, but to highly-trained Englishmen who worked for the Ministry of Defence in the branch known as MI5. (In fact the specially instructed interrogators were temporarily assigned to another classification, MI12, but to all intents and purposes they worked under the command of the Director of Intelligence in Northern Ireland, David Eastwood, himself a member of MI5) .
Some of these details may be inaccurate. The true location of the interrogations at Ballykelly in Derry was kept secret for many years. The military interrogators were probably not directly employed by MI5, which had itself ceased to be a part of the War Office military intelligence structure decades earlier.
Yet it is significant that Winchester, a journalist who Headquarters Northern Ireland set out to cultivate, was able to identify Eastwood's name and position.
Eastwood was certainly intimately involved in the administration of internment. In August 1971, he was the source for MOD estimates that 50 per cent of the Provisional IRA leadership in Belfast had been detained  He represented HQNI at an MOD meeting on internment on 11 February 1972, alongside Brigadier Marston Tickell . An account of the meeting records that 'D of Int was concerned at the bad affect of any release on on the Intelligence Organisation - especially of sources' . [DEFE 24/1215, Col GS MO4, 14 February 1972.]
HQNI's cooperation with the RUC in resisting internee releases was in contrast to the approach of the UK Representative in Northern Ireland, the Foreign Office diplomat Howard Smith . When Smith was appointed head of MI5 in 1977, he was denounced by his predecessor, Michael Hanley, for being 'too ingratiating to the minority community'in Northern Ireland and 'spending more time with the cardinal than any one else' . This may be a direct reference to the debate over internment, of which Cardinal Conway was a strong critic.
The terms of reference for the Director of Intelligence required him to liaise with the UK Representative, but the documents suggest this did not go as smoothly as intended. Certainly, 'David''s evidence to the Bloody Sunday Inquiry that he was unaware of MI6 activity in Northern Ireland does not suggest a closing working relationship with members of the UK Representative's staff . Among them was Frank Steele, an MI6 officer who received representations on internment from the SDLP during the course of 1972 .
These conflicts may be one reason why the advent of direct rule led to the appointment of a Director and Co-ordinator of Intelligence based at the Northern Ireland Office, and drawn initially from MI6 rather than MI5 .
MI5's role in the military escalation of the early 1970s may have ended in a temporary setback in a bureaucratic turf war, but it resulted in no lasting accountability.
That is perhaps not surprising. Intelligence agencies are supposed to be adept at exercising influence by informal means. What is remarkable is the extent to which that capacity shaped supposedly collegiate relationships within government. When it came to internment and deep interrogation, MI5 left the Army and the RUC to carry the can.
The Army, however, appears to have created its own provisions against this outcome. This took the form of a memo compiled by Brigadier J. M. H. Lewis (Brigadier General Staff (Intelligence) Defence Intelligence Staff) on 27 August 1971 as 'an insurance against future developments' (DEFE 24/1215, 27 August 1971) .
This comprehensively documents the role of MI5, the Home Office, and Sir Dick White in the policy of deep interrogation, recording:
- The first request for interrogation training from the Northern Ireland government came on 17 March 1971, at the outset of Sir Dick White's visit there.
- White emphasised the importance of interrogation training, and of Whitehall assistance to the RUC, in his report.
- MI5 officials at an MOD meeting on 24 March 1971 supported the establishment of an interrogation centre in Northern Ireland.
- The Director of Intelligence [Eastwood] supported RUC Special Branch's application for interrogation training assistance.
- The Director of Intelligence personally briefed Northern Ireland Prime Minister Brian Faulkner about interrogation techniques for an hour on 11 August 1971.
- 'Finally, I have it on hearsay from Mr James Elliott (MI5) that DGSS [Director General of the Security Service - Sir Martin Furnival Jones] briefed Sir Philip Allen, Home Office, about interrogation on 9 Aug 71.'
Lewis' message to posterity appears to be that MI5 was up to its neck in deep interrogation. If the European Court of Human Rights is to get to the truth of the five techniques, it could do worse than asking for the minutes of that meeting between Furnival-Jones and the Home Office.
 Ian Cobain, Cruel Britannia: A Secret History of Torture, Portobello Books, 2012, p.137
 Thomas Hennessey and Claire Thomas, Spooks: The Unofficial History of MI5, Amberley, 2009, p.580.
 Ibid, p.579.
 Evidence of MI5 officer 9004, Historical and Institutional Abuse Inquiry, 1 July 2016, paragraph 117. <https://www.hiainquiry.org/sites/hiainquiry/files/media-files/M15-D219-MI5-Officer-9004-Rev-RO.pdf>.
 Christopher Andrew, Defence of the Realm, The Authorized History of MI5, Allen Lane, 2009, Section E, Chapter 3, Counter-Terrorism and Protective Security in the Early 1970s.
 Evidence of 'David', Bloody Sunday Inquiry, 17 February 2000. <http://webarchive.nationalarchives.gov.uk/20101017070039/http://report.bloody-sunday-inquiry.org/evidence/K/KD_0002.pdf>
 Simon Winchester, Northern Ireland in Crisis: Reporting the Ulster Troubles, Holmes & Meier, 1974, p.171. Nigel West, Historical Dictionary of British Intelligence, Scarecrow Press, 2014, p.192. On Eastwood's career, see his obituary in the Daily Telegraph, 9 December 2010.
 National Archives DEFE 24/1215.
 National Archives CJ3/99.
 Margaret Urwin, A State in Denial: British Collaboration with Loyalist Paramilitaries, Mercier Press, 2016, p.23. On Herbert's previous MI5 career, see Calder Walton, Empire of Secrets: British Intelligence in the Cold War and Twilight of Empire, William Collins, 2013, p.208.
 National Archives CJ3/99.
 Simon Winchester, Northern Ireland in Crisis: Reporting the Ulster Troubles, Holmes & Meier, 1974, p.171.
 National Archives DEFE 24/1214.
 National Archives DEFE 24/1215.
 National Archives DEFE 24/1215, Col GS MO4, 14 February 1972.
 National Archives DEFE 24/1215. Minutes of a meeting at the Home Office, 11 February 1972.
 Christopher Andrew, Defence of the Realm, The Authorized History of MI5, Allen Lane, 2009, p.553.
 DEFE 24/1215. Steele to Woodfield, 24 July 1972.
 For another view of this event, see Christopher Andrew, Defence of the Realm, The Authorized History of MI5, Allen Lane, 2009, p.621.
 DEFE 24/1215. J. M. H. Lewis, BGS (Int) DIS to Military Assistant to Vice-Chief of the General Staff, 27 August 1971.