President Barack Obama said the relationship between the U.S. and Britain is ‘the strongest that it has ever been’ as he welcomed David Cameron to Washington in a lavish ceremony at the White House.

On a sun-drenched South Lawn, packed with 7,000 guests – including children from both nations – the Prime Minister basked in the warmth of the friendship offered by the U.S. president.

Mr Cameron returned it in kind, hailing examples of Anglo-American co-operation in war, diplomacy, science and business and describing Britain and the U.S. together as ‘the united states of liberty and enterprise’.

The extravagant ceremony, complete with 19-gun salute, a review of troops and marching fifers in colonial-era uniforms, was a far cry from the more low-key welcome offered to Mr Cameron’s predecessor Gordon Brown shortly after Mr Obama’s arrival at the White House, when the new president was keen to signal that his interests were directed towards Asia.

Now seeking re-election with several years experience of military co-operation with the UK in Afghanistan and Libya, Mr Obama was emphatic about the enduring value of what he terms the transatlantic ‘essential relationship’.

He added: ‘Our alliance is essential, it is indispensable to the prosperity and security that we seek not only for our own citizens but for people around the world.’

He won laughter from the Prime Minister and the crowd by slipping into British English to tell Mr Cameron: ‘We are chuffed to bits that you are here, I’m looking forward to a great natter, I’m confident that we are going to keep the relationship between our two great nations absolutely top notch.’

Both leaders were keen to stress how they had deepened their personal relationship with a trip to watch basketball in Ohio Tuesday night.

Mr Cameron joked that he had learnt some new words – ‘alley-oops, brackets and fast breaks’ – and might even install a hoop in 10 Downing Street.