Cook back, but what else would change?

Let's play fantasy politics. It is early September and Labour MPs have been called to an emergency meeting where the sole business is the election of a leader to succeed Tony Blair. Amid lamentation - some of it genuine - the PM has announced he is standing down. It is widely assumed that he will succeed Kofi Annan at the UN, following the secretary-general's sudden decision to retire on health grounds. Blair had staved off a parliamentary revolt just before the long summer recess, but his collapse in the polls has sealed the fate of his premiership.

For weeks, Gordon Brown has been refining "Plan Raith Rovers" - the shape of his first administration. He and his adviser Ed Balls flew to Cape Cod for a weekend tryst with John Prescott, and later there were bilateral talks near Heathrow with Jack Straw. Robin Cook's rehabilitation was settled by his agreement to act as "the man in the boiler suit" who warned Blair that he risked losing a vote of confidence among Labour MPs if he did not stand aside.

Brown will make changes in the cabinet, if only to stamp his authority even more firmly on a government already largely of his making. So he will make Alistair Darling the Chancellor. The former far-left activist who handed out leaflets at railway union meetings has proved a steady hand at Transport. What is more, he knows when to put up his hand in cabinet.

Yet Brown also wants to preserve continuity with the Blair years, so as to sustain the coalition of voters that swept the Great Helmsman to power. So Jack Straw is left at the Foreign Office to placate the ancien regime, and as a reward for coming over to the Brown camp at the right time. John Prescott remains head of the Office of the Deputy Prime Minister for the time being, but cedes the deputy leadership of the party to Robin Cook, whose role in the velvet coup was so critical. The new troika of Brown-Cook-Straw will lead the party into the spring 2005 election.

Beneath them, the changes will be subtle, if not cosmetic. Patricia Hewitt stays at the Department of Trade and Industry and Margaret Beckett at the Department for Environment, Food and Rural Affairs. In comes Yvette Cooper as Health Secretary. Prudence dictates that Brown has to solve the John Reid problem, which he does by offering him the job of Chief Whip. Wisely, but with as bad a grace as only he can muster, Reid accepts. Nick Brown, despite speculation that he would return to his old job as Chief Whip, goes to the Department for International Development. The Education Secretary, Charles Clarke, having nailed his colours firmly to the mast of a sinking ship, is replaced by the sharp-brained Ruth Kelly. Brown can genuinely say that his cabinet is a ministry of all the talents, but especially women. His only act of political savagery is to sack Geoff Hoon and replace him at Defence with Peter Hain. At a stroke, he punishes Hoon for his role in the David Kelly affair and overloads Hain with departmental responsibility, so that the devil cannot find work for idle hands. Tessa Jowell becomes Leader of the House - more than fair compensation, some say, for staying out of the final scrap.

Of the outer circle, only Charlie Whelan returns, as Lord Whelan of Dulnain Bridge, a roving envoy with special responsibility for Scotland. Peter Mandelson is appointed governor of Ascension Island. Westminster watchers search in vain for a guiding political principle. There isn't one. There is no obscure Aussie cleric or Mystic Meg in his make-up. Having imbibed a sense of decency during his childhood in a Scottish manse, he puts into action the ethical values of his father, Reverend John Brown. The new leader was an admirer of the 1920s Clydesider "Red" James Maxton, but not a disciple. Nor, for all his reading of economics, is he a devotee of the dismal science. His 1975 reformist Red Paper on Scotland broke new ground "He isn't influenced," said an associate. "He influences others."

The only question that neither Brown nor the Brownites wish to hear (much less answer) at this stage is: "How will things be different?"