As you walk to the entrance of Stormont Castle, you cannot escape the gaze of Sir Edward Carson, the arch-unionist who declared in 1913 that the Protestants would not "give an inch" to their Catholic neighbours. His statue today, defiant as ever, now guards one Martin McGuinness. He sits in the castle behind Carson, in a slightly messy office, working on the official papers of the government of Northern Ireland.
McGuinness has had a roller coaster of a fortnight. At last, he has been allowed to take up his office in the House of Commons, where he has raised the Irish flag. He has given oral evidence to the Saville inquiry about his role in the Bloody Sunday disturbances 30 years ago. And in his spare time, he has continued to run the province's schools in his capacity as education minister. His hair is greying, but he looks perky and his forehead is unlined.
How did it feel to take up his office in the Commons? "It wasn't that big a day," he shrugs. But come on - wasn't there a bit of him that wanted to gloat? "A bigger occasion for me was when I first went to Bangor as education minister . . . People were absolutely intrigued that this boy from the Bogside could come to Bangor in [Protestant] County Down and be education minister."
McGuinness is generous with his praise of the British Prime Minister for keeping the peace process show on the road. "Tony Blair has made a good contribution to the cause of peace in Ireland. He has made a great effort to understand it. He has great empathy with the need to resolve the conflict." In 1997, he was still describing John Major as "an arch-unionist". Does he think that Blair is a unionist at heart? He shakes his head. "He has been instrumental in bringing about devolution. We went through a torture mill to get an agreement to have devolution here . . ." He thinks that, "within his capacity as British Prime Minister, he is committed to the Union, but I detect a real openness to the idea that the people of Ireland might at some stage in the future vote for unification". He repeats this point when probed: Blair has "a very open mind" about where the Good Friday Agreement might lead.
However, McGuinness plainly loathes one of the Prime Minister's closest friends. Speaking of Northern Ireland secretaries past and present, he says: "Both Mo Mowlam and John Reid are very different to Peter Mandelson." He smirks bitterly. "I think that Peter Mandelson, particularly in relation to the issue of policing, made a huge mess of it. He allowed himself to be manipulated by the securocrats within the British establishment. That's why we have this awful mess at the moment," he says, referring to disputes over policing.
Mowlam might have shown herself to be "somebody who was not perfect" - for example, by allowing Orangemen to march down the Garvaghy Road - "but at the same time she was prepared to listen and she had a very, um, humane approach to people". He smiles at the memory, and I suspect that somewhere at the back of his mind he can hear the dull slap of a wig hitting a table.
John Reid "isn't as extrovert as Mo would be", but he "has a good heart . . . Like everybody else, he's learning all the time and I think that he clearly has shown himself to be someone who is very well disposed towards the peace process." McGuinness believes that the biggest issue confronting Reid is the reform of policing. Nothing shows the need to reform the police service in Northern Ireland more, he thinks, "than the revelations in the last few weeks about Omagh". He lists a number of police failures to achieve justice for the Catholic community in recent months . He ends his fiery comments by quoting the Belfast coroner, speaking in court in January, who described the conduct of the service in one particular case, under the leadership of Sir Ronnie Flanagan, as "a disgrace".
There is one major figure in the peace process whose absence is clearly keenly felt. "Bill Clinton was one of the greatest presidents that we've seen. He was involved in the peace process in the very beginning, and he not only showed himself to be knowledgeable about Irish history and Irish-British relationships, but also he was very sympathetic to the idea of resolving conflict."
Nobody could call George W Bush "know-ledgeable". So how does McGuinness feel about the new administration? He avoids my eye and folds his arms tightly. "The Bush administration has made its own contribution to the search for peace," he says vaguely, "and we have an ongoing relationship with the administration."
But he is openly critical of Bush on another issue. McGuinness has not been slow to notice that the images emerging from Guantanamo Bay are reminiscent of the days of internment. Many of his friends and comrades were held in such circumstances, a memory that clearly bites at him. "I think, on the island of Ireland, people will be very concerned by what they're seeing . . . The pictures that we saw, of prisoners manacled [by their] hands and feet, who were blindfolded and subjected to sensory deprivation techniques, have to be a source of great concern." The days when his friends were subjected to this kind of treatment are very much a closed book for McGuinness, at least as far as discussion goes. When I ask if he regrets that the Brighton bomb did not kill Margaret Thatcher in 1984, he hesitates. "I think it's regrettable that anyone lost their life in the course of the past 30 years. No matter who was killed, it's a tragedy for that particular family." But does he not, deep down, still wish that the IRA had pulled off that particular job? "I won't get into this debate about individual circumstances. Margaret Thatcher could sit there now and talk about how pained she was by events; I could talk about how pained I was by the murders on Bloody Sunday, about the way the hunger strikers were allowed to die in 1981; the unionists can cite events; the people in Britain can cite events . . . but what does it all amount to? How does that bring us to a resolution of the conflict? There has been a lot of pain on both sides . . . The predominant emotion now must be that the peace process succeeds, and we never again see what we've seen from all sides."
He is angry that "there are people within unionism who want to bring down the agreement. That's why I think that the IRA decision to put arms beyond use is such a courageous decision. In October last year, the IRA saved the peace process."
Can he envisage a situation where the unionists would succeed in bringing down the peace process? "Yes. That's what we saw [them try to do] on the day we elected David Trimble and Mark Durkan . . . There are unionists in this building who are determined to bring down the power-sharing approach, make no mistake." If they succeeded in doing that, would the IRA end its ceasefire? He prevaricates. If that happened, "we should be less concerned about what the IRA would do, and more concerned about how the British government would respond to any successful venture by unionists to bring these institutions down."
Yes, but in that eventuality, would the IRA resume the armed struggle? "There's a tiny constituency out there who want to bring this down. They're not all unionists. Some of them are republicans who reject the peace process." What would the IRA do if the peace process broke down? Is there a plan B? "If . . . the institutions collapse, would I be any more understanding or sympathetic towards what these people [who take up arms] are doing? The answer is no."
Is he hurt when IRA and republican dissidents accuse him of being a traitor? "Not at all. I have always been part of the republican movement and I will always be part of the republican movement. I don't think many people accuse me, although I am aware of a few individuals who really represent nobody." Real anger is visible on his face. I would not like to be one of those "few individuals". McGuinness growls that "there is every opportunity for those who accuse me of betrayal to put themselves before the people, as I have done, and seek support for their point of view . . . I increased my majority by 5,000 six months ago."
He clearly loves his job as education minister. Yet there is concern that, as one of the most sectarian figures in the Northern Ireland cabinet, he is not doing enough to facilitate integration. He has a vested interest in Catholic schooling, so he is not tackling the problem of single-faith schools on either side. The Free Presbyterian Church (the creation of Dr Ian Paisley) runs seven schools in Northern Ireland. Their virulently anti-Catholic interpretation of the Bible, they assert, "informs every lesson". I ask him if this worries him. "No. What worries me more is that those schools can use corporal punishment." He explains that the Northern Ireland Assembly is making moves to ban it. All well and good, but isn't the great popularity of single-faith schools in Northern Ireland (only 10 per cent of children are educated in integrated schools) a huge factor in perpetuating sectarian divisions? "People have a right to educate children in the fashion that they want . . . We are dealing with a legacy and a history here."
McGuinness does believe, however, that he has a responsibility to "improve and facilitate" integrated education. "I have done more to promote integrated education than any other minister in the history of the state," he says. "So I think that sends a very clear message to everyone." But what exactly is the message? He insists, after all, that "the absence of integrated education is not the reason why we have sectarianism within our society. The reason we have sectarianism is because of Partition in 1921." It doesn't help, does it, that Catholic and Protestant schoolchildren never meet or form friendships? "You have to move forward sensibly . . ." He smiles. "People are entitled to choice."
When he speaks like this, he sounds instinctively political - and I realise how far Martin McGuinness has come. Only 15 years ago, when he was widely believed to be the IRA's commander of "Free Derry", he repeatedly stated: "I am a soldier, not a politician." Yet here he is, waffling like politicos the world over.
I challenge McGuinness again on what would happen if the peace process failed. He looks straight at me. "I am actually full of hope and optimism for the future." He pauses, and says, almost to himself: "When I go through the quiet, reflective periods in my own home, late at night, I'm not concerned by the prospect that everything's going to collapse. I'm concerned by how we can keep it going." Maybe I've fallen for devious republican propaganda, but I think I believe him.