The efforts to reach an agreement in the Stormont talks kept Tony Blair in Belfast from Tuesday afternoon until teatime yesterday.
Indeed, his spokesman revealed that the prime minister had not slept at all from the beginning of the last intensive round of talks until he left for Madrid last night, a period of some 36 hours.
Mr Blair, a man of slight physique, looked somewhat pale and worn last night as he announced the successful conclusion of talks. He was standing alongside the Taoiseach, who had also had a long night without rest. Mr Ahern's black tie reminded journalists of his recent loss of his mother, Julia, which must have added considerably to the stress he was under.
Asked about the events of the "Long Night's Journey into Peace", Mr Blair's spokesman said there were "an awful lot of meetings".
The person the prime minister met most often and for the longest time was his Irish counterpart, but the two of them also had lengthy meetings with other participants and kept in constant touch with the chairman, Senator George Mitchell. Witnesses said a whole forest of paper was consumed making drafts and counter-drafts, amendments and counter-amendments.
The key meeting, however, was the tripartite encounter between Mr Blair, Mr Ahern and the Ulster Unionist leader, David Trimble, shortly after the Taoi seach's arrival on Wednesday evening.
This came about 36 hours after Mr Trimble had appeared to reject outright Mr Mitchell's draft text for a settlement, produced in the early hours of Tuesday morning. That rejection had plunged the talks into crisis: Mr Trimble spoke three times to Mr Blair on the telephone on Tuesday morning, and by early afternoon word, came that the prime minister was flying to Hillsborough Castle.
The relationship between Mr Blair and the UUP leader is a good one by all accounts. They are at ease in each other's company and, if anyone was going to talk Mr Trimble out of his rejectionist stance, it was Mr Blair. The unionists see Dublin as unashamedly pressing the constitutional and the nationalist case and it is important to them that "their" prime minister is at least willing at all times to listen to unionist concerns.
The first real break in the crisis came with the arrival of Mr Ahern. "Bertie the Rainmaker" clearly said enough to Mr Trimble to reassure the UUP leader it was worth his while staying at the table. Sources close to Mr Blair said the meeting was "very, very significant".
The prime minister's spokesman said the Blair-Ahern connection was one of the key relationships in the talks. They had "very sincere mutual regard" and worked very well together.
Mr Blair's view of Mr Ahern is that "he's got great calm". Both men were "detail merchants" with the ability to get on top of a complex brief like Northern Ireland. "They are both good at communicating with people that are not of their ilk." The two leaders were in constant contact through the night, sometimes only briefly when they got together to "crack" some new difficulty.
Mr Blair also consulted John Hume to draw on his "expertise, experience and wisdom".
The extra-mural involvement of President Clinton was also important, perhaps even crucial in steadying unionist nerves on decommissioning yesterday afternoon. There had been previous contact with the president in the early hours of yesterday morning, when Mr Blair spoke to Mr Clinton twice by telephone, at 4 a.m. and 4.10 a.m.
Indeed, Mr Clinton may well decide to visit Northern Ireland on or around May 15th to lend his support in the referendum, and there has even been talk of Hillary Clinton coming for a longer stay. Mr Blair himself will probably want to canvass, too.
A Strand 1 agreement reached at 3 a.m. yesterday between the SDLP and the UUP on an executive committee with 12 ministers to run Northern Ireland also gave the process a critical boost. Hardly able to contain their excitement, it was clear from the demeanour of SDLP insiders that they regarded this as perhaps the crucial step to an agreement.
Although anxious to join his wife, Cherie, their three children and his mother-in-law on holiday in Madrid, Mr Blair stuck with the hard grind. He reportedly consumed no alcohol, had only regular infusions of tea and a modified version of the famous "Ulster Fry" yesterday morning.
While the governments had been stressing the importance and near-immovability of the April 9th midnight deadline, one talks participant said it "kinda came and went".
By about 5 a.m. yesterday, the deal at last seemed to be coming together. A new dawn for Northern Ireland, so to speak. Participants got a sense that "we were in shape to get the document done". The new layout in the plenary room at Castle Buildings apparently facilitated an improved relationship between the parties. With the help of screens and easy chairs, an area was created in the room for delegates to relax and hold conversations with some semblance of privacy.
There was also a small bar and some of the loyalist delegates brought their friends in for a drink on the historic night. As the Rev Ian Paisley arrived outside to stage a protest, some of these visitors apparently left to heckle the DUP leader as he tried to give a press conference.
As the night wore on, delegates grew more and more tired, but not the Taoiseach. According to one observer, Mr Ahern showed "phenomenal energy. He didn't take a single break". Despite the lateness of the hour, the level of activity was rarely less than frenetic.
At about 6 a.m. Lord Alderdice gave a brief press conference and clearly found difficulty believing that so many yawning gaps had been bridged.
The Alliance leader said it was "quite remarkable". Another participant said it was "quite an extraordinary night"." Even those who had predicted the deal would be made found difficulty in the end believing that no wheels fell off the wagon - but it's early days yet.