So who will take over from Campbell?

Tony Blair next week notches up another political record - the longest continuous period in power of any Labour Prime Minister. But now some of his closest aides are peeling away. Anji Hunter, a friend since they were at nearby schools, was the first of the original Gang of Four advisers to leave his inner circle.

She quit last summer, after a bout of feuding, for a quieter life at BP at double her salary.

Sir David Manning, Mr Blair's valued foreign policy adviser, has had more hours of "face time" with him than almost any other civil servant since September 2001. He will be next to go when he departs soon to be the new Washington ambassador.

That leaves only Alastair Campbell, Mr Blair's powerful media and strategy adviser, and Jonathan Powell, the curly- haired former diplomat who is No10 chief of staff. One or both will be gone this autumn.

Mr Campbell is ready to go after his disastrous one-man war with the BBC. He is said to have told the Prime Minister in private yesterday and to have considered walking out as early as today.

The pair agreed he would wait a few months, at least until his name is cleared of "sexing up" the Iraq dossier. A not guilty verdict on this charge is highly likely when the intelligence and security committee reports on the affair just before the Labour conference.

He is also honour-bound to wait until the Hutton Inquiry reports into the death of scientist Dr David Kelly before beginning work on his "pension" - as he calls his assiduously-kept diary.

"He is very angry, and a lot of people are telling him to calm down, but he is also depressed and tired," said a colleague. "He is determined not to go under a cloud." Mr Powell is rumoured simply to be ready for a change of career.

Downing Street says reports that he has already decided to resign are untrue but Mr Powell's wife Sarah is known to be keen for him to do a less gruelling job.

Little wonder Mr Blair has chosen to fly to Barbados for a family holiday rather than stay to celebrate when, a week tomorrow, he breaks Clement Attlee's record for unbroken Labour longevity at Downing Street - notching up six years and 94 days at No 10.

But, although prophets of doom ask how he can cope without the four, Mr Blair has an outer circle of aides ready and waiting to move into the centre. Their names are mostly unknown outside the Westminster village but they are all trained in the New Labour school of discipline and tribal loyalty.

One is Mr Blair's political secretary, Pat McFadden. A slimlybuilt Scot, he was Mr Powell's deputy before moving to Labour headquarters for the last election and then leaving for fresh fields. He was recalled in October when No10 was in a panic over the rise of union militants and needed someone with good contacts.

A likeable figure, Mr McFadden is already a key player because of his expertise and popularity with union leaders, Left-wing MPs and leading activists. He is one of the last remnants of John Smith's leadership team and so skilled in office diplomacy that he was called in to act as Peter Mandelson and Gordon Brown's go-between when they were not on speaking terms.

But, although he will fill part of the vacuum, he cannot replace Mr Powell altogether. Mr McFadden, unlike his ex-boss, lacks a civil service background.

Instead the job will be split up. The title chief of staff would probably go to Jeremy Heywood, said to be Mr Blair's favourite career civil servant. He is the PM's principle private secretary but carries the extra title head of policy directorate - a reward for turning down offers of promotions.

The big difference is that, instead of a Gang of Four, it will probably take seven or eight people to fill the gap in No10, say insiders. "You cannot just give someone the same job title as Alastair or Jonathan and expect them to get on with it," said one. "In Whitehall, it is not your title that's important but what you are 'copied into', and a newcomer might find they were getting only a fraction of the material."

So Mr Campbell's job - director of strategy and communications - would also probably be split up.

The task of rebuilding relations with the BBC and the press could be handed to a civil servant. Tom Kelly, a tight-lipped Ulsterman and one of the two official spokesmen for the PM, will move up a rank if Mr Blair decides to go for a non-controversial "anti-spin" solution.

But Mr Campbell's role as Labour leader's spokesman would require a political appointee. Phil Bassett, a former Times industry correspondent turned special adviser at No10, is already a seasoned briefer of the press and may step up. But he is also tipped to leave to work for Constitutional Affairs Secretary Charles Falconer.

Peter Hyman, Mr Blair's main speechwriter, could take over Mr Campbell's strategic planning duties.

One of the big questions is whether any of the rising stars will be given the unique special powers wielded by Mr Powell and Mr Campbell to order civil servants around.

A former adviser says such powers are less needed now that Campbell and Powell have reorganised Downing Street and much of Whitehall jumps instantly to the PM's wishes.

"Everyone now knows the most powerful words in Whitehall are 'Tony wants' - whoever takes over will benefit from that culture of efficiency".

Anji Hunter's place in the inner circle has been taken over by her old rival Baroness Morgan - now a rising power, although she carried some of the blame for the botched reshuffle.

There is still no word on a replacement for Sir David Manning as the top foreign affairs aide. Whoever Mr Blair chooses, it will give a clue about his own state of mind.

"If he picks potential high-fliers who need time to learn the ropes, it means he is digging in for the long haul," said a former minister. "If he lets the civil service fill up the gaps with their own kind, it will be a sign that he has run out of energy - and is ready to hand over to Gordon Brown."