A document has emerged which reportedly contains Chancellor Gordon Brown's "price" for agreeing to let Tony Blair become prime minister.
The apparent pact is the stuff of political folklore
The Guardian claims a six-paragraph note shows that Mr Brown won a "guarantee" from Mr Blair that he would follow a Brownite economic and social agenda.
The paper suggests this was the cost for allowing Mr Blair's accession to Labour leader and then prime minister.
The document is said to have been drafted by former cabinet minister Peter Mandelson the day after an infamous private meeting in 1994 between Messrs Blair and Brown at the Granita restaurant in Islington.
As Westminster folklore goes, the supposed "deal" between the pair saw Mr Brown holding back from running for the Labour leadership following John Smith's death.
Both recognise the importance of the partnership they have built up and of the Smith legacy of unifying the party and making use of all its talents
In return, Mr Blair was supposed to have agreed that he would at some stage stand down to make way for Mr Brown to become prime minister, reports the former has always denied.
But the paper says that the note is the first written proof of a formal pact between the two.
The original typed draft said: "In his Wales and Luton speeches, Gordon has
spelled out the fairness agenda - social justice, employment opportunities and
skills - which he believes should be the centrepiece of Labour's programme and
Tony is in full agreement with this and that the party's economic and social
policies should be further developed on this basis."
Mr Brown admitted on BBC's Breakfast with Frost on Sunday that he had replaced the words "is in full agreement with this" with "has guaranteed this will be
pursued", thus strengthening his own grip on the party's policymaking
The note makes no mention of when or if Mr Blair would step down as Labour leader and prime minister in favour of Mr Brown, the paper says.
The chancellor is respected as undoubtedly Mr Blair's most able minister, winning widespread praise for masterminding Britain's economic stability.
But there have been questions recently over his predictions for growth - downgraded last autumn - and whether the huge increase in borrowing announced last summer is sustainable.
Monday's decision on the euro will be crucial to the chancellor's future.
If he calls for indefinite delay on joining the currency - and he is widely seen as the most euro-sceptic minister in the cabinet - some commentators believe the prime minister might lose patience.
But The Guardian says the note it obtained tried to cover over disagreements between Mr Blair and Mr Brown by insisting that they shared a common agenda.
"What makes this possible is the strong overlap of their approach to policy and their shared thinking on the key issues," the briefing said.
"Both recognise the importance of the partnership they have built up and of the Smith legacy of unifying the party and making use of all its talents."