This year's Brighton conference promises yet another stirring instalment in the Blair-Brown saga. Their relationship is unique. Never before have the top two in Government been yoked together for so long - with one convinced the other's job should be his. When they work together, there's no stopping them: but when they don't - all hell can break loose.
Labour's former leader Neil Kinnock, who first promoted both men and comes to see them on his regular visits from Brussels, says: "They are bound to collide. If they had the sweetest marriage ever known to humanity they would be bound to collide. But there would be a synthetic quality about the Government if these guys didn't ram each other occasionally."
Although the Prime Minister often accuses the media of treating politics as soap opera, the true-life drama played out between the No 10 neighbours and one-time best friends has had more twists and turns than a soap scriptwriter would dare to imagine.
In making my TV documentary I discovered, in a case of life imitating art, that both men are themselves fans of American TV soaps. But while Mr Blair enjoys The West Wing, the supposed hard man in the relationship, Gordon Brown, turns out to be a devotee of 30-something romantic comedy series Friends.
Territorial jostling between Blairites and Brownites in government began on the day after Labour's historic 1997 victory. Mr Brown's former spin doctor, Charlie Whelan, was having a beer and a smoke with some friends in the downstairs offices at No 11 when Cherie Blair walked in. "Cherie comes and says, 'What are you doing in my house?' And I don't think she quite realised that this was actually bits of Gordon Brown's house too," Mr Brown explains.
"She was quite shocked. I don't think Tony quite explained to her that they're only having the flat, but the door to the flat is off the State room and offices downstairs - so she thought she was having all that as well."
The unusual domestic living arrangements of the Downing Street neighbours prefigured a seven-year long battle for supremacy. On the one side, the Brownites - the Chancellor and his tight-knit group of acolytes determined to keep control over every economic decision to themselves. Up against them, the Blairites - the Prime Minister, his press secretary Alastair Campbell and a powerful group of special advisers.
The Treasury was Gordon Brown's citadel of power and command centre. By tradition the most influential ministry in Whitehall - with a finger in every other departmental pie - under Gordon Brown, the Treasury became even more dominant, with the Chancellor determined to hold Mr Blair to his pledge that Mr Brown would have unprecedented power in economic matters. Although the Prime Minister is officially the first Lord of the Treasury, the Brownites took to referring to their man as the real prime minister - calling Tony Blair the figurehead president.
Another insider who saw the way the Blair-Brown relationship operated was a millionaire businessman who worked for five years in the Cabinet Office as a senior adviser to the Prime Minister, Lord Haskins. "At one point, Gordon Brown was introducing the Working Families' Tax credit which was a very radical tax and very complicated," said Lord Haskins. "And I'd been involved in trying to work out how it was going, how it would be implemented in practice and the Prime Minister decided he wanted to know something about this working family tax credit - which didn't seem unreasonable. And he asked just if the Chancellor would come in and explain to him how it worked.
"The Chancellor didn't think this was a very good idea but he arrived at No 10 with his laptop and gave quite a brusque demonstration of what was behind the working families' tax credit. And when he finished, the Prime Minister said: 'Can I ask a question?' And Gordon said, 'No!' And he shut his laptop and went off. That sort of area was not for Prime Ministers to be dwelling on - that was his territory."
"You know there's a battle going on and people support or go to one side or the other and I think that is crippling for a government," says Mo Mowlam, who was a cabinet minister for the whole of Mr Blair's first term. "As a cabinet minister you have to wait and see what comes out of the sausage machine. You are not part of the decision."
For the past 10 years, the creative tension in their relationship has curbed the radical instincts of the two men - Mr Blair's free-market approach and Mr Brown's egalitarianism. The result has been a kind of third way, which, although it has often meant a bumpy ride for the PM and Chancellor, has shown that a Labour government can run a successful economy. Although, like a fractious married couple, the question of who gets the house is still all-consuming for them, when one of them does eventually get written out of the plot, almost all of us could find ourselves worse rather than better off.
Michael Cockerell's documentary on the Blair-Brown relationship is on BBC 2 tonight in 'Do you still believe in Tony?' at 7.25pmReuse content