By Andrew Marr
BBC political editor
Archaeologists have dug up inscriptions from Roman London which refer in clear terms to the feud between Tony Blair and Gordon Brown...
Mr Brown is said no longer to trust Mr Blair
Well, not quite; but it has been going on for a very long time.
We know how and why it started, right at the beginning of Mr Blair's leadership. We know why it worsened so dramatically last year - because the chancellor thought the prime minister had promised him that he would quit No 10.
Thanks to numerous leakers, "friends", hacks and authors, we know a remarkable amount of detail about their rows - where they happened and even what was probably said.
Nobody now pretends these stories are fictitious, or merely journalistic hearsay.
Both Mr Blair and Mr Brown have said they won't comment publicly on old stories; which is a different matter from saying they are untrue.
Mr Blair says he would not negotiate over his own job. In the Commons, abandoning his previous position of not giving a running commentary on the feud, he said that Mr Brown had not, in fact, told him he would never believe a word he said.
The fortified wall around private conversations between the two men, conversations about as sensitive as any that could be had in government, has become rickety, has been breached in places, and seems too thin to preserve real secrets.
And that is the real problem.
There is less authority at the top than ever before
After recent moves from No 10 which seemed to humiliate Mr Brown, and the brutal frankness with which his camp has leaked details of Mr Blair's alleged perfidy, how can the two of them have an honest, private talk in the future?
Each will fear the other will repeat what is said.
But if they cannot have a proper confidential conversation, they cannot have a proper political relationship either.
And if that is so, it means that, for all practical purposes, the creative partnership between prime minister and chancellor is over. They can paper over the cracks in the few months before an election. They can talk with pride about the economic record. But they cannot look and plan ahead together.
The word "if" appears in the previous paragraph. It is still, just, possible for the two men to prove that there is a way back, but hardly anyone in the government expects that.
Instead, if Labour wins the election well, the likeliest outcomes being discussed by other ministers are either that the prime minister steps down quickly, or that he demotes, or even dismisses, Mr Brown.
Labour faces an awful dilemma here. It both seems true that Mr Blair will not want to carry on with Mr Brown; and also that Mr Brown is overwhelmingly still the likeliest person to replace Mr Blair.
This seems like the transition from hell, and while the most senior politicians in the country are struggling with how it can be managed, the Labour back benches are beginning to reassert themselves.
There is less authority at the top than ever before - witness the extraordinary dressing-down by MPs at this week's Parliamentary Labour Party meeting.
So Labour members are readier to rebel, refuse to accept this or that; and the administration's authority flakes away.
For any government with such a large majority, this is an unusual situation. For one ahead in the polls, months from an election, it is unprecedented.