A day of political speed-dating as Brown sizes up the presidential candidates

Gordon Brown meets with presidential hopeful Barack Obama yesterday (AP)

There was an unmistakable twinge of envy among European diplomats yesterday as the three American presidential candidates and their secret service details made their way up Massachusetts Avenue for separate meetings with Gordon Brown at the residence of the British Ambassador, Sir Nigel Sheinwald.

The joggers along Embassy Row were agog. On one side of the street, Pope Benedict XVI's motorcade was coming out of the Nuncio's residence even as Barack Obama was arriving to meet Mr Brown. Such is the Pope's pulling power that he shut down both the House of Congress and the Senate yesterday because more than 100 politicians wanted to attend his first mass in the US, at the national baseball stadium.

The Catholic swing vote is crucial but Mr Obama, Hillary Clinton and John McCain happily skipped Holy Mass in favour of meeting Gordon Brown. It was Stalin who acidly asked, "how many divisions does the Pope have?" and a variant of that question will have been on Mr Brown's mind as he probed the three presidential candidates and, later on, President George Bush, about American force levels in Iraq and Afghanistan.

Mr McCain was the easy one, since he has already declared that US forces can stay in Iraq "for the next 100 years". Mrs Clinton, who voted for the war, now wants to start bringing troops home in her first 60 days in office. Mr Obama is committed to withdrawing all combat brigades from the country within 16 months of entering the White House. There is plenty of wriggle-room in each position and everyone accepts that promises made on the campaign trail are often forgotten when a candidate crosses the threshold of the White House.

Nobody knows who will be sitting in the Oval office next year, or what the state of US foreign policy will be. To judge by their statements on the campaign trail, the US may be embarked on a radical course of rapid-fire change set by Mr Obama. He has offered to hold face-to-face meetings with the heads of "rogue" states such as Iran, and has promised to quickly close down the Guantanamo Bay detention centre while banning torture by the US military.

Rapid action on climate change is also high on his agenda, with the aim of locking the US into a binding new agreement at the United Nations summit in December 2009.

The no-nonsense style of foreign policy under Mrs Clinton may be easier to predict. But there could also be a return to the paralysis of the Clinton years, where external affairs were dictated by domestic opinion polls – preventing, for example, US intervention to halt the genocide in Rwanda.

Under a president McCain, whose mindset helped bring about the war with Iraq, the policies of the Bush era are expected to continue, but under more competent management. There might even be armed conflict with Iran.

Mr Brown's priority – aside from pro forma meetings with President Bush – was getting to know Mr Obama. He has been itching to develop a rapport with the man from a wing of the Democratic party with which Mr Brown is already on good terms from years of holidaying in Martha's Vineyard.

On the face of it, they share a commitment to helping the developing world and working through bodies such as the United Nations and the international financial institutions. But, unlike Mrs Clinton and Mr McCain, a president Obama may not reflexively think of Britain in times of trouble.

Born in Hawaii and schooled there and in Indonesia before going on to attend Yale and Harvard, Mr Obama's world view is strikingly different to his opponents. Should he win the Democratic nomination and go on to take the White House, the "Obama doctrine" promises the most sweepingly liberal US foreign policy in decades.

Inexplicably, no meeting between the two had been arranged before yesterday, something Mr Brown described as "an accident".

As he watched the Obama motorcade thread its way through the pillared gates of the embassy residence, an EU diplomat described the achievement of getting all three candidates to show up on the same day as "amazing". The diplomat added: "It just shows what the UK role here in Washington is, there is no way that we, or even the Germans could have done the same."

To avoid showing favour, the three candidates each received 45 minutes with the Prime Minister. Even achieving that was a minor miracle, as Mrs Clinton and Mr Obama are in the death throes of the struggle for the Democratic nomination. They will meet again during next Tuesday's Pennsylvania primary vote.

The British connection

Hillary Clinton

The valleys will be in full voice for Mrs Clinton if she is elected to the White House. She confided to Gordon Brown that her grandmother would have been "very proud" of the Welsh rugby team's Six Nations success. She also has English ancestry – her grandfather, Hugh Rodham, emigrated from Co Durham.

Barack Obama

The Berkshire town of Bracknell does not spring to mind when Barack Obama is mentioned, but some of his greatest admirers live there. Mr Obama says he has family "of every race and every hue, scattered across three continents". And from Bracknell he is no doubt being closely watched by his stepmother Kezia and half-sister Aum.

John McCain

John McCain admires a stiff upper lip. He told Gordon Brown that some of his favourite generals are British. In 1966 his parents were dressing for a dinner party in London when they learnt that he had been shot down while on a bombing mission over Hanoi. They went anyway, never telling the other guests.

For rolling comment on the US election visit: independent.co.uk/campaign08