Whatever Gordon Brown and John Prescott said to each other in the back of that Jag, the "Loch Fyne summit" looks set to enter the history books as a key moment in New Labour's evolution.
By Nick Assinder
BBC News Online political correspondent
Like London's Granita restaurant before it, the Scottish oyster bar - at least its car park - has become the focus of speculation about Tony Blair's future or, more accurately, the end of his leadership.
Blair faces mounting leadership gossip
Anyone who regularly prowls the corridors, bars and restaurants of Westminster knows there is only one topic of conversation at the moment - when and how the prime minister will go.
It seems senior ministers are positioning themselves for life after Blair.
Or as Mr Prescott, put it, the tectonic plates are moving. And that usually precedes an earthquake.
Time is up
Ministers are all rallying round in public, of course but there is little doubt that old feuds - between Robin Cook and Gordon Brown, for example - have been patched up and new alliances are being made.
Backbenchers, meanwhile, are becoming increasingly nervous about the safety of their own Commons seats. If Tony Blair really has become an electoral liability, many of them will pay the price.
And at the centre of all this activity sits the near Buddha like figure of the deputy prime minister, John Prescott.
If anyone is likely to deliver the message to the prime minister that his time is up, that his party has lost confidence in him, and that he should go now, it would very likely be Mr Prescott.
Prescott shared back seat with Brown
The deputy PM knows he is near the end of his parliamentary life, even if he insists he will fight the next election, so has no career axe to grind.
He may be a more natural Brownite than Blairite, but few can doubt his loyalty to his leader. He also remains well plugged in to the grassroots party and, crucially, the unions.
So, the fact that Mr Prescott and Mr Brown apparently spent almost two hours in a car park discussing whatever they discussed is absolutely bound to provoke speculation about the succession.
This may, of course, all be the media-hyped "fluff" that Downing Street insists it is. And we have been here before, albeit in a less frantic atmosphere.
Blair's future tied to Iraq
But few really believe that
And no one doubts that the single biggest issue that is driving all this movement, and which is threatening to define Tony Blair's premiership, is Iraq.
Tony Blair is irrevocably tied to the unfolding situation in that country and, to that extent, events are out of his control - as the murder of the head of the Governing Council has displayed.
Even many of his supporters are now expressing serious doubts over the original decision to go to war and whether there were credible plans for the peace.
Mr Blair is insisting he will stick it out and many would be deeply concerned if he simply walked away from the conflict now.
Equally, there are those who would urge Gordon Brown to keep his powder dry. Why, they ask, would he want to take over the government before Iraq's path to peace and democracy had been secured?
There are some big dates looming - notably the European and local elections on 10 June, the handover to the interim Iraqi government on 30 June and Iraq elections in January.
And, of course, there is the annual Labour party conference in September.
If the prime minister gets through all those landmarks in one piece, then it is a near certainty he will make it to the general election.
But these are highly dangerous times and only the foolhardy would claim they can predict with any certainty what will happen over the next few months.