The Northern Ireland Secretary hinted at the covert intelligence advice she had been given in her statement, when she said did not believe "these recent events represent a decision by the organisation to return to violence".
"That is the key," said one ministerial source. "If it had been the considered view of her advisers that there was going to be an organised return to violence, she would not have made that decision."
Sources in Dublin said she had been in impossible position. "If she had been replaced by Peter Mandelson, he would have found himself in the same position," said the source. "The Unionists say she is giving a licence to killing. The nationalists would have said she had killed the peace process, if it had gone the other way."
The intelligence advice tipped the balance, leaving her with little option but to declare the overall ceasefire holding - in spite of clear breaches.
The RUC Chief Constable, Ronnie Flanagan, made clear in public he believed the IRA killed Charles Bennett, a taxi driver in Belfast. The IRA denied that the killing of Mr Bennett, an alleged informer, was a return to military operations.
The Northern Ireland Secretary rejects the suggestion by hardline Unionists that her decision was tantamount to sanctioning killing. She points out that her remit was to consider the prisoner release scheme. She could have slowed the release of inmates, but that could have led to the collapse of the Good Friday peace Agreement.
David Andrews, the Irish Foreign Minister who had been consulted by Ms Mowlam, yesterday praised the "integrity and decisiveness" of her decision. The Irish government advised her not to suspend the release of prisoners. Unionists said Mr Andrews had let the "cat out of the bag" on Monday with his unguarded remarks at a press conference. He said that in his judgement there had been no breach of the ceasefire, implying that the decision had already been reached. But the British Government is adamant that she did not make up her mind after meeting the Irish minister. She had consulted the General Officer Commanding the Armed Forces in Northern Ireland, Lieutenant- General Sir Hugh Pike, for his security assessment. She also waited for more information on the smuggling of arms from Florida by a group claiming to be members of the IRA.
The Irish special branch and the US Department of Justice appear to have advised the Northern Ireland Office that there was no evidence of a concerted effort to re-arm the IRA. Downing Street and the Prime Minister - who was ending his holidays in France this week - were kept fully informed by Ms Mowlam. It was a lonely decision to take. But she was not alone in taking it.