For Mr Blair, it was also a severe personal blow. He has invested months of time and effort in the attempts to bring the two sides to agreement.
"He doesn't get angry," said his official spokesman. "He feels sad that at a time when you have devolution in Scotland and Wales and economic regeneration, Northern Ireland is not going to be getting that."
Mo Mowlam, the Secretary of State for Northern Ireland, also looked and sounded exhausted yesterday when she delivered a statement to the Commons. Her replacement in Mr Blair's Cabinet reshuffle in a fortnight will have the task of breathing fresh life into the process.
There were increasing signs at Westminster that Ms Mowlam, who is loved by her own back bench, will be moved to a campaigning role in the party, and could be replaced by Peter Mandelson, who sat in a prominent place on the front bench below the gangway during the second reading of the ill-fated Northern Ireland Bill.
Mr Mandelson would command the respect of the Ulster Unionists who want a new secretary of state with the Prime Minister's ear. He has actively damped down speculation of his return to the Cabinet after resigning in December as trade and industry secretary over his loan from a fellow minister, saying that it would be too soon. But few of his critics in the Cabinet would begrudge him the bed of nails at the Northern Ireland Office.
He would be able to take the load off the Prime Minister, who has increasingly taken over the negotiating role from Ms Mowlam, as the Unionists became more hostile, culminating in the warning by David Trimble, the Ulster Unionist Party leader that she was out of touch with Unionist opinion.
Observers questioned Mr Blair's strategy for forcing the pace by continually setting deadlines and wondered why he had allowed this week's negotiations to become a crisis. The answer was supplied by his official spokesman: "All the big movements in progress in this have tended to have come when you have a dramatic, high-profile event, and then you can get a break thorough. It has worked in the past, but this time it has not worked."
Mr Blair told the Cabinet that it was important to avoid recriminations, and to focus on the way forward.
There is deep frustration in Downing Street at the failure to break through the "thin crust" of the political elites in Ulster to reach the vast majority of the people who overwhelmingly voted "yes" to the Good Friday Agreement in the referendum. That frustration led to the idea of holding another referendum, this time restricted to the North. Mr Blair's official spokesman yesterday dismissed claims that a second referendum would be held, but it appears not to have been finally ruled out for the long term.
If nothing has happened by the next deadline, by May 2000, a second referendum may seem like a last chance at peace.Reuse content