SF's key man in Stormont tells Northern News Editor Dan Keenanhe saw the deal with the DUP from a long way off
Martin McGuinness sits easily in the buttoned leather of his Deputy First Minister's office and calls it as he sees it.
"I believe this is a very defining moment," he states over his undrunk mug of tea. "This is the most defining moment of all. May 8th will be the mightiest of all leaps.
"It will see us effectively declare our intention to work together in the interest of all the people we represent. That's incredible!"
The war is over and the unlikeliest of compromises has been reached involving the former IRA man and the firebrand leader of Protestant unionism. But the deal which stunned so many across Northern Ireland and beyond came as less of a surprise to the Derryman who has been at the sharp end of republican negotiations with the British government since early 1972.
"I have known now, for something like 18 months, that there was a mood change within the broad unionist community, the people were becoming increasingly anxious to see the back of the direct rule ministers.
"They wanted to see their own ministers. And obviously I built up very close connections to people who are close to both the Ulster Unionist Party and the Democratic Unionist Party.
"I think I've had a good accurate assessment of where, not just the community are at, but in terms of where the politicians were at, whether or not they were going to do the business.
"So it's been my sense for the last two years that they were going to do the business. It was a matter of constructing the circumstances to actually see that happen."
It's an eyebrow-raising claim, that Sinn Féin's chief negotiator had his finger on the unionist pulse for so long. So he repeats: "Well, what I mean is that I have impeccable sources close to both the DUP and Ulster Unionist Party and these are people who are well placed to paint a picture of where both parties are at.
"But obviously, of most interest was where the DUP were at, given their prominence within the broad unionist political scene. And obviously these people, too, knew what the heartbeat of the unionist community was effectively saying, and it's been clear to me for some considerable time, that there was increasing pressure mounting on unionist politicians to effectively stop the messing about and to get into government."
On one thing at least, Martin McGuinness believes Ian Paisley - when the DUP leader says he will share power, he will. He speaks kindly of the cordial and business-like dealings between them. It will be a getting-on-with it relationship and the "battle a day" phrase is never employed.
The unlikely coalition will provide the good government and powersharing the people want after years of seemingly intractable peace processing, disappointment and setbacks, he believes.
"Sinn Féin and the DUP, led by Gerry Adams and Ian Paisley, have now crossed a Rubicon together. That, in many ways, undermines those out there who are ill-disposed towards what we are doing.
"I think the election results were clearly the people speaking out and Ian Paisley got overwhelming endorsement by the unionist people, and we got overwhelming endorsement from the nationalist/republican community. Anybody who sets their face against that is effectively walking into a wilderness, is going nowhere."
He "gives credit" to David Trimble for his efforts post-1998 when the Belfast Agreement was signed. But, and it's a very big but, Trimble failed "to fully embrace the type of change that the Good Friday agreement envisaged, because he was fixated, he was effectively like a rabbit in the headlights of the Democratic Unionist Party".
That was then - this is now. He recognises the extent of public surprise at the momentous leap forward and, in a sense, tackles the question on many people's lips even before it is asked.
"I think that many people have looked on at all of this with considerable amazement. And I suppose justifiably, people wonder why this couldn't have happened before."
He moves to answer his own question: "In many ways a lot of it was to do with the way in which the DUP managed its contributions to this over a period of time . . . We've finally come to a point where the DUP have had to look at the contributions that republicans have made. For example, dealing comprehensively with the issue of arms, making it clear that the war was over and then the mighty debate, probably the biggest debate of all, the policing debate.
"How that ended up at the ardfheis, the vindication of the Sinn Féin position by the electorate and it becoming quite clear to the DUP that, as they had said publicly, that they wanted to go into government and that they were a devolutionist party, so it became very clear to them that the only way into government was alongside Sinn Féin."
Pressed on the questions about why it took so long, about the necessity of 30 years of conflict, about the possibility of a politically counter-productive war, he answers with questions of his own.
"At the end of the day if we're going to start to impose the blame for all of it, then let's put the blame where it needs to be. Maybe it needs to be all over the place, you know - the British government and unionist political leaders can't escape their share of the blame for not having addressed the issues of concern of many people within society at a time when they were marching for civil rights on the streets."
"You know when questions are posed to republicans about what was the last 25 years all about, well I say to myself, what was partition about, what was unionist rule in the North about?"
He says he is always reminding himself about a story told to him by his political adviser Aidan McAteer. He is the son of Hugh McAteer, and a nephew of [ former Nationalist Party leader] Eddie McAteer.
"The only piece of legislation the Nationalist Party got passed in this building was the Wild Birds Act in all the time that they were here," McGuinness recalls.
"Now I'm walking into an administration with five Sinn Féin ministers, an SDLP minister - well capable of putting in place all sorts of legislation and taking all sorts of very important decisions in the interests of not just republicans and nationalists, but everyday within the community. So, what was 800 years of British involvement in Ireland all about?
"I mean the difficulty is that when people pose that question it's almost as if they say - well the blame for the past 25 years rests with republicans who embarked on armed struggle against the British army.
"Don't people who pose that question airbrush out of history what was happening on the streets of Derry before there ever was an IRA?
"The RUC were beating people in their houses and people weren't allowed to walk the streets, there was massive repression and so, as has been the case in other conflicts throughout the world, at some stage against that type of violence imposed on citizens, people are going to respond."
Rather than blaming republicans for the violence, he urges critics of the IRA to realise who has made the significant moves for peace.
"At the end of the day the people who broke the vicious cycle of conflict and violence were the republicans. It was Sinn Féin and it was the IRA - the IRA decision to call the cessation of 1994. Obviously this was the spark that lit the flame in the peace process to set us all on the journey to this place."
That journey in a sense ends tomorrow at Stormont and both Martin McGuinness's wife of 32 years and his 83-year-old mother will be there to see it.
It seems not to matter about a Paisley handshake: "These are great times for everybody, we're all very conscious of the past, but I'm more conscious than everyone to ensure that whatever we do in the future is better than anything we did in the past. I think that there are better days ahead."