The outcome of those negotiations with his difficult, belligerent, big- hearted deputy could determine the success or failure of a Blair government and both Blair and Prescott are aware of it.
Prescott has always had the capacity to withdraw from the "Blair project" if he believed it was going too far in the modernisation of the Labour Party. He has complained about the pace of change but he has not objected to the principle of change.
Prescott's critics on the left of the party who believe he has given away too much, and in the Conservative Party who see him as a political dinosaur, misunderstand the man, and have fallen for the easy stereotype.
The Prescott the public sees is the bluff Northerner, blunt as a fist, a chip on both shoulders, with vowels as flat as a cap, bruising for a fight. There is no doubt that Prescott is tough. As a boy at sea he had to be - life as a young organiser in the seamen's union in Liverpool was no place for the faint-hearted. His father, Bert, told me that young John learnt how to box to protect himself against intimidation.
I had access to Prescott's papers, his family and his friends, although my book is an unauthorised biography. They are an amazingly loyal bunch. Former seafaring friends, the Cunard stewards with whom he used to serve coffee to the blue-rinse ladies on their trips to America, would not speak to me without first checking with "Johnny" to make sure it was all right. Even then, they were guarded about what they would say about the antics of young Lothario from Chester who bore a striking resemblance to Marlon Brando in On the Waterfront when he was a youth.
They still keep in touch with the deputy leader of the Labour Party, 30 years after he left the ships, and in December they held their annual reunion. He has tracked down a ship-owners' model of their old ship, the Britannic, which they are hoping to install in a maritime museum on Merseyside. It was the same with his friends at the Commons. They have formed a screen around him, which could be opened only with his say-so.
What is it in Prescott that inspires such loyalty? It is partly, no doubt, that they wish to avoid his bark, either down the telephone or in person. But it is also because they know the vulnerable, private side of Prescott.
His second son, David, a journalist, who looks remarkably like his father when he was in his twenties, says Prescott can speak to a crowd of 3,000 supporters without flinching. In fact, he enjoys the experience - but he will not ring up a restaurant to book a table. Prescott says he fears rejection.
Thousands of children like Prescott failed their 11-plus but none has been quite so scarred by the experience. He has frequently told the story of the girl who sent back a love-letter when he had failed the exam, with the spelling errors corrected. Nothing could have been quite so crushing as that rejection. I tried to find her, but he is keeping her identity secret. His brother Ray can't remember her. Ray went on to grammar school, while John went to a secondary school at Ellesmere Port.
His mother, Phyllis, a life-long Labour supporter, says the class-warrior was worryingly shy at school. Part of the problem was his syntax, or lack of it. Some have suggested it might be a form of verbal dyslexia.
His closest trade union friend, Rodney Bickerstaffe, believes his mind races ahead, jumping from one thought to another. There is little wrong with his capacity for intellectual thought. He regards himself as one of the original modernisers, who was having fresh ideas before the Blairites were out of short trousers.
Pauline, his wife, says he is the HG Wells of the modern Labour Party. The refusal of the "intellectuals" to recognise Prescott's contribution to the modernisation of the party is a continuing source of his frustration, which causes his occasional outbursts in the press.
My starting point for writing the biography was rooted in the late Eighties, when I discovered that Prescott was quietly pushing forward a change of policy that would allow British Rail to raise private finance for investment in rolling stock and track. To Prescott, it seemed a logical solution to a problem of Treasury stringency, but breaking down the Treasury orthodoxy took years.
John Major was tentatively pushing at the same policy, and now claims parentage for the Private Finance Initiative, but it was Prescott's idea. Similarly, Prescott came to the conclusion at the same time as Blair that accepting the Social Chapter would also mean an end to the closed shop - giving people rights also meant they had a right not to join a trade union.
His experiences at sea convinced him of the need for pre-strike ballots long before they were endorsed by Blair. He cut his teeth addressing pier- head mass meetings of strikers in the Sixties, which were open to intimidation. Such meetings also taught him that it was vital to bring the men with you, if you were to act as a leader. It was the reason why, years later, when he fell out with Neil Kinnock over his own autocratic style of leadership, he told the Labour leader: "Courage is not enough - you have to bring the party with you."
His readiness to think unconventionally caused some surprises for his tutors at Hull University where, as a mature student in the mid-Sixties, he took an economics degree. His tutors found he was quite prepared to throw in a bit of poetry with his work on the theory of inflation, and he once bumped into Philip Larkin in the street. He asked whether he could attend one of Larkin's poetry seminars, but Larkin looked down his nose at Prescott and walked on.
Researching the book, it came as a shock to the spin-doctored system to see a BBC video of the 1982 party conference when Benn, Scargill and Kinnock - then a hairy education spokesman - were in the ascendancy. Under a slogan "Peace, Jobs, Freedom" speakers wearing CND badges and woolly sweaters engaged in uncomradely points of order with the "comrade chair", Judith Hart.
The debates were inward looking, with comrade Healey scoring points off comrade Scargill. Viewers were made to feel like voyeurs not voters. It was a reminder of how far Blair has broken down the class war barricades and opened the Labour Party to ordinary people more concerned with mortgages and good schools than passing resolutions at party meetings.
It casts an interesting side-light to the relationship between Blair and Prescott to discover that when they stood on the platform together on 21 July 1994 as leader and deputy leader, their wives had never met before. They come from different generations, and different backgrounds, and the Prescotts are not part of the London dinner party scene.
Prescott had felt at ease with John Smith's leadership and Smith's sudden death was a terrible personal blow. Prescott had delivered his now-famous speech in support of Smith at the party conference in Brighton in 1993 during a debate on "One Member One Vote" democracy in the party. Smith had privately threatened to resign if he had lost. Friends said Prescott never felt patronised by Smith, and they understood each other. That was all changed when Smith died of a heart attack in May 1994.
Blair's determination to press ahead with rewriting Clause IV of the party's constitution could have caused the first real crisis in their alliance. Prescott was against the reform, but he was won round, and when he was persuaded of its virtues, he became a crucial factor in selling it to the party. His disagreements with Blair since then have not been about the direction in which he is taking the party, but about the pace of change. Prescott's loyalty was strained to breaking point in early 1995 when he was kept out of the "magic circle" for an important strategy meeting. Since then, he has insisted on being kept informed.
Prescott is a great conspiracy theorist. A picture on his living-room wall reminds him of how cruel the plotters can be. It is a print of the official painting of the House of Commons, when Thatcher was Prime Minister and Kinnock leader of the Opposition. It was done from a photograph, taken when Prescott was sitting on the front bench. In the painting he appears on the second row, on the so-called "loyalty bench", demoted, he is sure, on the orders of someone in the leader's office.
Above all, Prescott has been keen to show Blair that his loyalty is absolute, once it has been earned. I had assumed that Prescott's hero would be Nye Bevan, the Welsh left-wing firebrand. But reading modern political history at Ruskin College, Oxford, Prescott adopted Ernie Bevin as his hero. The working-class Labour MP who rose to become foreign secretary in the great reforming 1945 Attlee Government was Prescott's perfect role model. Prescott sees himself in the role of Bevin to Blair's Attlee, providing sage advice and indefatigable support, when necessary. There is no question in Prescott's mind that Blair has achieved great things for the Labour Party, but he would prefer it if the engine driver would listen to the voice from the guard's van a little more.
About 12 months ago, Blair warned the Shadow Cabinet that unless they were united, they would risk losing the election. Prescott heeded the warning. His last public remonstrance was last August, when Prescott said in an interview with me for The Independent that he thought the election should be fought on substance, not style.
Since then, Prescott has been keeping loyally to the task of seeing Labour elected. He is not about to explode, like some long-extinct volcano, or lead a peasants' revolt once the election is safely won. He will not play George Brown to Tony Blair's Harold Wilson, but there are some sticking points to his loyalty. He would not allow Labour's links with the unions to be severed without a fight, and he is wary of those who have floated the idea of a coalition with the Liberal Democrats as a bastion against Labour's own left wing in government.
There is continuing doubt about Prescott's likely role in government. Blair ducked the question again on the BBC Breakfast with Frost show at the weekend. There is talk about Prescott being made Home Secretary; it is one of the high offices of state, and it would keep him out of Gordon Brown's hair.
If Labour does win, and Prescott gets the call to Number 10, he may ask to be made First Secretary and Deputy Prime Minister, like Michael Heseltine. In my view, he has earned it.
'Fighting Talk', Colin Brown's biography of John Prescott, will be published by Simon and Schuster on 3 February (pounds 15.99).