Burgers and burning issues on Obama's UK visit
Bonhomie around the barbecue is a certainty.
In the garden of Number 10, the prime minister and the president will flip burgers, slap backs and show the world that they're chums - though there isn't much in their backgrounds to bind them.
One is a Hawaiian-born ex-lawyer and Chicago community organiser; the other's a former TV executive from the Home Counties who went to Eton.
There isn't a shared foreign policy ideology like that which tied the Cold War partnerships together or fuelled the alliance between Blair and Bush.
And, of course, one's a Conservative, the other a Democrat.
But after the tetchy awkwardness of the Brown-Obama relationship, this appears to be an easier fit.'Sentimental warmth'
Stylistically, Obama and Cameron are both pros at switching from insouciance to statesmanship.
Both seem at ease with themselves. And both practise the politics of pragmatism over dogma which, as they work through their to-do list (Afghanistan, Libya, security co-operation, counter-terrorism and the fallout from the Arab Spring), could help them find a common approach.
But is their relationship "special"? It's a phrase that has one former diplomat reaching for his revolver.
"We don't need tears of sentimental warmth," says Sir Christopher Meyer, Britain's former ambassador to Washington.
"Exhausted talk about a special relationship should be put out to grass."
Thanks to the Wikileaks cables we now know that US diplomats in Grosvenor Square also wearied of the pundits' preoccupation with the uniqueness of the UK-US alliance. One despatch from February 2009 said the frequent over-reading of perceived signals of tension would be "humorous if it were not so corrosive".
And last year, a report by the Foreign Affairs Select Committee urged Britain to be "less deferential" to the United States and put talk of the "special relationship" aside.
Here's why. The rapport between president and prime minister is often seen as a litmus test of how closely the countries are getting along. In fact, there's an infrastructure of intelligence-sharing, nuclear co-operation, commercial and cultural links that rolls on regardless.
And secondly, the US has "special" relations with a number of countries, from Mexico to Israel.
Nevertheless, on the eve of their meeting in Downing Street, David Cameron and President Obama have renewed their vows. In a jointly written newspaper piece, they say the UK-US relationship is "not just a special relationship, it is an essential relationship - for us and the world".
It's a warmer tone from the president, and one that will colour this crowd-packed, pageantry-filled visit.Global affairs
And what about the substance of their talks? Afghanistan is the key issue.
President Obama will announce a reduction of US troop numbers in July, and Washington is now stressing the need for talks with the Taliban.
The two leaders are likely to discuss how to move the diplomatic push forward, as well as the strained relations with Pakistan.
In Libya, a Nato mission that Britain nudged the US in to joining, a stalemate is setting in and Obama and Cameron will surely talk about what happens next.
The Arab Spring sprung without the US or Britain playing any part, but the aftershocks are of huge interest to the two countries.
They're also both still grappling with the fallout from the banking crisis.
David Cameron's a year ahead of the president with his plan to shrink the budget deficit and might offer some tips as they chew on their sausages.