The former British prime minister, Mrs Margaret Thatcher, when in power gave her personal approval to secret talks between British government officials and the IRA leadership in 1990, setting in a train a dialogue which led to the Northern Ireland peace process, which she now regularly denounces.
In one of her final acts before she was deposed as prime minister, Lady Thatcher allowed her Northern Ireland Secretary, Mr Peter Brooke, to talk to republicans through a secret "back channel" after MI5 advised the government that the IRA was looking at ways of ending its terrorist campaign.
The Guardian newspaper reports the disclosure of her involvement in today's edition.
The news will embarrass the former prime minister, who has always insisted she never talked to terrorists. Lady Thatcher, who was nearly murdered by the IRA in the 1984 Brighton bomb attack, also gave the go-ahead to the talks in the same year that republicans murdered her friend and close colleague, Mr Ian Gow.
Mr John Major, who faced severe embarrassment in 1993 when his government's role in the "back channel" was revealed, gives a hint in his new autobiography of his predecessor's role when he writes that Mr Brooke opened the channel in 1990. The Guardian learnt from officials who were at the heart of the process in the early 1990s that Lady Thatcher gave the go-ahead to the talks after MI5 told the government that the IRA was open to dialogue.
"It is rather ironic that it was Thatcher who gave the go-ahead, given her ferocious language at the time," a former official said yesterday.
Lady Thatcher's decision over the talks is an example of how her hardline public utterances as prime minister contrasted with moderate behaviour in private. In her autobiography she said she was wrong as prime minister to try to appease Irish nationalists. She is scathing about today's peace process and has condemned the British Prime Minister, Mr Tony Blair, for releasing terrorist prisoners, one of the main concessions in the Good Friday agreement.
The "back channel", which had existed since the early 1970s, was reactivated by Mr Brooke in 1990 when both the government and the republicans recognised that they would have to find a new way forward after the terrorism on the 1980s. Messages were passed between the two sides by a go-between, the "mountain climber".
In public, Mr Brooke also sent powerful signals to republicans. In his most important speech weeks before Lady Thatcher's fall Mr Brooke said Britain had "no selfish strategic or economic interest" in Northern Ireland.
The Guardian has learned that Lady Thatcher only approved the controversial phrase, which the Northern Ireland Office had been trying to use for years, after the end of the Cold War. It is understood she was reluctant to use such neutral language earlier because British nuclear submarines passed close to Ireland.
In his autobiography, Mr Major devotes a lengthy section to the "back channel" which makes clear that his Northern Ireland secretary, Lord Mayhew, gave a misleading account when the secret talks were revealed in 1993.
At the time, Lord Mayhew said Sinn Fein's Mr Martin McGuinness had initiated contact with a message which supposedly said "the conflict is over".
Lady Thatcher's office declined last night to comment on the secret IRA talks. A spokesman said: "We tend not to comment on government matters because we do not have ready access to papers."