In 1940, when Adolf Hitler's armies seemed certain to sweep across the English channel to invade the United Kingdom, Winston Churchill made a speech.  He described Britain's links with the United States as a "special relationship", tying in his country's fate with that of the US, hoping his powerful words and strong rhetoric would move those who opposed American involvement in what they saw as a European war.

Seventy years later, the phrase still frames US-UK relations.  It's trotted out every time the leaders of the two countries meet, and again it's been used extensively this week.  Yet the Americans have never regarded it as that special.

Famously, Margaret Thatcher and Ronald Reagan enjoyed a close relationship, shared by a common ideology, a common drive towards free markets and minimal state intervention.

Tony Blair was friends with Bill Clinton but seemed much closer to George W Bush. The two made unlikely soul mates.  Political opposites, they did however share religion and famously prayed together.

Yet in the sixties, Prime Minister Harold Wilson clearly condemned the US bombing of Hanoi and refused repeated requests to commit troops to Vietnam, while his successor, Conservative Edward Heath hated - and that's not too strong a word - President Richard Nixon.

Relationship in trouble?

And most recently Gordon Brown suffered snub after snub at the hands of Barack Obama. The Americans denied several requests for a face to face meeting. With Obama high in the polls and globally popular after his election, the troubled British Prime Minister was hoping some of the stardust might rub off on him.

Eventually the pair met for 15 minutes in a kitchen at the UN.  It was clear the special relationship was in trouble.

But then, to Barack Obama, the link with Britain has never been the most important. He sees China as significant strategically, economically and politically. If he wants movement in North Korea, it's likely to come through Beijing. He hopes Russia will help bring Iran to the negotiating table over its nuclear programme and in Europe, he recognises that Germany has the economic strength and so a large helping of influence to go with it.

David Cameron has been prime minister of the United Kingdom of Great Britain and Northern Ireland for just over two months. He has travelled to Washington for his first official visit.

While he shares little of Barak Obama's political ideology, both leaders are roughly the same age and are driven by making important changes domestically. They are linked through operations in Afghanistan, and while there are significant differences in the approach they would take in handling the global financial crisis, they are aware efforts to combat the problems have to be co-ordinated. 

There is also the growing issue of the release of the Lockerbie bomber Abdel Basset Al Megrahi.  David Cameron will face angry senators who want to know why the man convicted of mass murder over the skies of Scotland was released on health grounds.  Cameron will tell them the decision was taken by others, before he was in power and it was something he opposed. It is, politically, the best defence.

Cameron has been speaking openly and honestly about the nature of the special relationship, describing Britain as "junior partners" and insisting he will be "hard headed and realistic" in relations with the US.

For much of the US media, the arrival of David Cameron is really just another visit of another foreign leader, albeit an important player on the world stage.

The British media will follow every step, every word, every moment as a guide to the health of the relationship between the two countries and to see if after all these years, it's still special.