The Belfast Agreement apart, one of the outstanding features of the last British parliament was the close personal relationship between Tony Blair and David Trimble.
The relationship was formed in the days when they were more modestly known just as Shadow Home Secretary and Ulster Unionist leader. Mr Trimble apparently decided then it would be easier to do business with a Labour administration - for example on the question of a Bill of Rights, incorporating the European Convention. And, most crucially, he says, "to ensure that devolution to Northern Ireland happened within a United Kingdom framework".
Whatever the current or threatened crises in the peace process, Mr Trimble claims vindication. "That clearly has happened, and happened under a Labour government; it couldn't have happened under a Conservative government."
He does not dissent when I observe that he quite evidently trusts Mr Blair. "Well, he's a person that I do business with but I think he's been open with me. Of course things have not always gone as we expected and there are a significant number of people in Northern Ireland who feel that Blair misled them at the time of the referendum."
To which Mr Trimble offers his own retort that "the Prime Minister would be, I think, frank and say that some things did not work out as he expected at the time".
Not for the first time - on prisoner releases, and the failure to link that process to IRA decommissioning - Mr Trimble is content to lay the burden of blame at the door of the Northern Ireland Office, and of former secretary of state Dr Mo Mowlam.
William Hague, on the other hand, thinks Mr Blair is a phoney, prepared to say the opposite of the truth when it suits him. Presumably Mr Trimble acquits his friend?
"I shall not get into a controversy between Mr Hague and Mr Blair," comes the laughing reply. "I shall leave Mr Hague to do what he does as Leader of the Opposition and I shall not put any obstacles in his way."
Some Tories with serious misgivings about the direction of the peace process, of course, do consider Mr Trimble an obstacle. Often they lament their inability to "out-unionist the leader of the Ulster Unionists".
Mr Trimble will have none of it. "I think some Conservatives have used that as an excuse but it is necessary, as I have pointed out to them, for me to have a relationship with the government, whoever the government might happen to be."
Beyond the peace process, Tories repeatedly accuse New Labour of being ashamed of Britain. And they see the Blair devolution project as precursor to the break-up of the United Kingdom. Does the Ulster Unionist leader ever worry that Mr Hague might be right?
Mr Trimble remarks on the unusual trait which sees Britain as one of the few countries whose intellectuals "tend to think it's smart to be anti their own country". It's a tendency, he says, that also afflicts the Tory party, and which he divines even in Northern Ireland "because it is a British trait".
However, on the substantive point, he thinks the Conservatives mistaken "to assume devolution is somehow anti-British. I think devolution will strengthen the Union and is already doing so."
Some Conservatives suspect the speed with which Dublin established diplomatic missions in Edinburgh and Cardiff reflected an Irish Government calculation that devolution pointed to the eventual disintegration of the United Kingdom. Does that cause him any anxiety?
Mr Trimble says he doesn't know Dublin's view. But he cites the Scottish experience, where he sees devolution "eating away at the SNP and turning Labour into a unionist - small U - party". And he detects in consequence a shift in Irish policy "from one of trying to keep as far as possible away from anything British to one of close engagement" - with the Republic actually "being drawn back into a British orbit".
Conservatives also see the devolution project as the instrument of a Britain of the Regions, paving the way for a Europe of the Regions. Does Mr Trimble accept that British membership of the euro would be the stepping-stone to the European superstate?
"The point has been made of anybody who wants to create a united Europe is that the biggest thing they need to go for is not a single currency but a single language, which they'll never get," he replies.
So when Mr Hague presents this election as the last chance to save sterling - is it all a bogey? "Clearly, the Conservatives feel they're tapping into something quite important in the national psyche, which is there," he concedes. In fact "support for the European Community enterprise is diminishing in Britain for good reasons, and it is partly the disjunction between the European Community and the real Europe".
However, while there is something in that British psyche, Mr Trimble declares himself "sorry to say" that the Tories "don't seem to be addressing all the other issues the British public are interested in".
"I don't think the Conservatives can succeed by being a single issue party. They have got to address the concerns of the British people as a whole and present themselves as a credible alternative government, and I think they're having difficulty doing that."
So, assuming a Labour victory, how will Mr Trimble advise the people of Northern Ireland to vote?
First, he says, he is making no assumption there will be a referendum. But as things stand at the moment, "as far as I can see, any circumstances I can presently envisage . . . I would not support going into the euro. I think it's going to be bad for us economically as well as bad for us constitutionally."
And what does he think might prevent the Prime Minister calling a referendum? "Because the Treasury's economic tests have not been met and are not likely to be," comes an apparently very confident answer. But most people suspect the tests aren't real, that they could be deemed satisfied at any point suitable to the government?
The First Minister insists they haven't been met and "and they're not likely to be". Here, putting himself noticeably at odds with Mr Blair, he agrees there are huge political and constitutional issues at stake. "Of course there are, of course there are."
So does he think a country can give up its currency and retain its sovereign independence? "One thing that's absolutely clear is that if Britain goes into the euro then the British Chancellor will cease to go to international meetings like the G7," he ventures. Then a question of his own: "And do you think the Chancellor who runs the fourth-largest economy in the world is going to put himself in a position where he's the treasurer of a county council?"
Particularly a Chancellor who may . . . ? I start the question but Mr Trimble has anticipated me and is laughing again: "Who clearly has a keen interest . . ." he offers. Indeed, a Chancellor who has a keen interest in succeeding Mr Trimble's friend in 10 Downing Street? "Well yes indeed . . ." Mr Trimble laughs some more.
The First Minister is obviously monitoring the cabinet positioning on the euro with the greatest care. And it seems pretty clear that Tony and Gordon both can count on his friendship during New Labour's expected second term.
The final piece in this series, Frank Millar's interview with Rhodri Morgan, the First Minister of Wales, has been held over until next week