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What no one dares stop calling the Special Relationship has been defined down the years by images - Ronald Reagan and Margaret Thatcher dancing, George W Bush joking about sharing Colgate with a grinning Tony Blair squeezed into crotch hugging chinos and years later spinning a be-suited and grim-faced Gordon Brown around in a golf buggy.

Last May David Cameron and Barack Obama flipped burgers together at a barbecue in the Downing Street garden. The No 10 spin doctors thought they'd never do better, but tonight they believe they have.

David Cameron will become the first world leader to be welcomed aboard Airforce One by President Obama so that both men can travel to the crucial swing state of Ohio. The pin up of the global left and the leader of the British right will add the latest image to the photo album of the Special Relationship.

They'll be pictured doing what millions of Americans do every week - chewing the fat with a friend whilst watching the game. Not just any game, mind you. It'll be Obama's favourite - basketball.

Good for a President wanting to reassure American conservatives in election year. Very good indeed for a prime minister wanting to appeal to the centre ground and who won't meet any of the Republican contenders for the Presidency.

Over the next three days there will be more - a White House garden party with hundreds of guests, a banquet with still more and even a 19 gun salute. All the trappings, in other words, of a state visit save the absence of the Head of State herself.

Given that Her Majesty has no plans to visit the US the White House are treating Mr AND Mrs Cameron to a little of what the president and the first lady enjoyed on their recent visit to the UK.

Another reason for the warmth of the welcome is, according to the US Ambassador to London, that the prime minister would be the first person the president would choose to call in an international crisis. And there are quite a few of those looming over the next year.

In public the talk is of sticking to the agreed plan in Afghanistan - the end of combat operations sometime in 2013 - the withdrawal of troops in 2014. However, privately the two leaders will want to dwell on the fallout of the killing of 16 Afghan civilians by a US soldier and the killing by the Taliban of 6 British soldiers in a single explosion.

'Quite a claim'

They will want to examine what can be done to topple Syria's President Assad without the military strikes which brought down Libya's Colonel Gadaffi.

And crucially they will need to consider what to do if Israel ignores their urging to give diplomacy with Iran a chance. Last week President Obama had the opportunity to look Israel's Prime Minister Netanyahu in the eye and judge how close he is to launching a war. David Cameron will want to know what he saw.

Then there is, of course, the small matter of the economy and a recovery now under way in America and barely under way here which could be halted in its tracks by a rise in oil prices.

In a joint article for Tuesday's Washington Post the two leaders write of a relationship which is not just special but "essential - to our nations and the world... a partnership of the heart, bound by the history, traditions and values we share".

"With confidence in our cause and faith in each other" - they write - "we still believe that there is hardly anything we cannot do."

Quite a claim but with the agenda they are confronting you can see why they must hope it's true.