It is one conclusion that can be drawn after a momentous week in which the strained 'TB-GB' relationship finally snapped. "Tony doesn't regard Gordon as his best successor, " one Blairite minister said. "He sees him as his only successor."

Blair is furious with Brown at what he is convinced was an attempted coup by the chancellor's supporters. Even if he didn't start it, the Blair camp believes he could have halted it on Wednesday, and prevented the resignation of eight junior ministers, if he had spoken up for Blair.

While Brown supported Blair when he broke his silence on Thursday, the PM pointedly declined to praise or endorse the chancellor during his apology for the week of turmoil.

The hints about tensions between them have been there over the years. The biggest clue came when Blair told last year's Labour conference:

"Every time I've ever introduced a reform in government, I wish in retrospect I had gone further." It was a barbed reference to differences with Brown which prevented him going further. One Blair ally claims the chancellor "could have been prime minister by now" if only he had thrown all his weight behind Blair's reform programme.

According to this version of events, Blair wrote a private letter to Brown in January, promising to quit around his 10th anniversary in Downing Street and offering to let his broad timetable become known. In return, he wanted Brown's full support for the policies he wanted to push through in the meantime.

Brown reacted positively and there seemed to be the makings of a "stable and orderly transition". But the deal fell at the first hurdle when they clashed over pensions reform.

The Blair camp claims Brown scuppered their emerging agreement on the transition. The Brownites say it would have been irresponsible for their man to sign off a package he believed the country could not afford, and to give Blair a blank cheque to push through anything just to speed up his departure.

When the friends-turnedrivals held two tense meetings on Wednesday, Brown sought Blair's endorsement as his successor . . . in part to discourage a 'stop Gordon' candidate from running against him in the leadership election. The chancellor also sought a bigger say over government decisions before Blair departs. But Blair apparently dismissed what allies called a demand for a "dual premiership", which amounted to a Brown veto.

One minister admits there has been a "conspiracy of silence" in the Blair camp over Blair's real views about Brown because they were so incendiary. That period seems to be over. But allowing such doubts to surface is playing with fire.

The Blair camp has no viable alternative candidate to oppose Brown. It hoped David Miliband might run, but he has backed the chancellor.

Alan Johnson might stand for both deputy and leader but is still relatively inexperienced.

John Reid is tough but lacks strong support among MPs, as does Alan Milburn.

Charles Clarke is heavyweight enough to run but would be in a much stronger position if he had remained in the cabinet. Perhaps Blair regrets sacking him as home secretary over the foreign prisoners fiasco and maybe Clarke regrets not accepting another cabinet post.

In his current mood, Blair is probably inclined to endorse nobody as his successor. That will be seen as giving tacit support to the anti-Brown brigade, a campaign without a leader.

The file marked "Brown" kept at the Tory HQ must be bulging with examples of what Brown's Labour "colleagues" say about him. His allies fear attacks on him from his own side will only help one person: David Cameron.

In the dark days of opposition, Blair and Brown were among the first Labour figures to learn that a party obsessed with internal squabbling will alienate the voters.

Last week, both men seemed to have forgotten it.