The relationship between David Cameron and Mitt Romney got off to a bad start today as the prime minister rebuked the Republican candidate for talking down the London Olympics.
Cameron was responding to a US TV interview in which the man who delivered the 2002 Salt Lake Winter Olympics cited concerns over strikes and security in London and said it was "hard to know just how well it will turn out".
Speaking ahead of the opening ceremony tomorrow, Cameron hit back: "We are holding an Olympic Games in one of the busiest, most active, bustling cities anywhere in the world.
"Of course it's easier if you hold an Olympic Games in the middle of nowhere."
The spate comes amid continued irritation in the Romney camp at Cameron's gushing praise for President Obama during a recent visit to swing state Ohio.
Romney told American television reports about London were "disconcerting" and "not… encouraging" but he adopted a more sympathetic approach during a meeting with Labour leader Ed Miliband in parliament this morning.
"It is impossible for absolutely no mistakes to occur," he told gathered journalists.
"Of course there will be errors from time to time, but those are all overshadowed by the extraordinary demonstrations of courage and character shown by the athletes. As soon as the Games begins, we'll forget about the organisers."
But the Republican candidate raised eyebrows later when he told journalists he enjoyed looking out of "the backside of Downing Street". It is thought he was referring to the garden.
Minutes later he committed another gaffe when he admitted he met the head of MI6.
David Cameron, speaking at a press conference at the Olympic park, said he was keeping his "fingers crossed" that all would go according to plan.
"Our fingers are crossed for everything from events to the weather to transport infrastructure and everything else. But from where I stand we're set for a remarkable few weeks for everything," he said.
Barclays funding row
Romney's trip had attracted controversy even before it had begun, after he triggered claims of racism for flagging up "Anglo-Saxon" links between Britain and the US.
And the former Massachusetts governor flew into a storm over funding from Barclays.
Eleven MPs have signed an early day motion calling on the bank and its directors to stop funding the Republican challenger and instead focus on restoring the bank's credibility in the wake of the Libor scandal.
Barclays insists the donations are from individuals and do not reflect the views of the bank itself.
"All political activity undertaken by Barclays' US employees, including personal fundraising for specific candidates, is done so in a personal capacity, and not on behalf of Barclays," a spokesperson wrote to MPs.
Bob Diamond, who recently endured a bruising encounter with MPs on the Treasury committee just days after being forced to resign as Barclays boss, has been a lead fundraiser for Romney and John McCain before him.
Funding forms a core component of Romney's visit. An exclusive fundraising dinner in Mayfair tonight will see guests pay between $50,000 (£32,000) and $75,000 (£48,000) for a ticket to boost his spending in the campaign tonight.
Hidden tensions in party leader meetings
Romney has reasons to be wary of both Cameron and Miliband.
The Republican's aides are still sore after Cameron joined Barack Obama on a visit to swing state Ohio, complete with a state dinner in Washington. During the trip, many felt the prime minister went overboard when he praised the US president's "moral strength" and "fundamental decency".
While Romney and Cameron would agree on most economic matters, the two men are politically distant on social issues such as gay marriage, especially given the decisive rightward drift of the Republican party in recent years.
"While I am on foreign soil... it would be remiss of me to criticise any other government's policies," Romney said during his meeting with Miliband.
Their brief discussion saw the pair face a cultural chasm. Miliband's background as the social democrat son of a Marxist father is a world away from Romney's experiences as a Mormon right-wing businessman.
The American said that he agreed with Miliband on "our commitment to peace" and their joint interest in prosperous economies.
Both men apparently support the Boston Red Sox baseball team, however.
Miliband, who beat Cameron to the Elsyee Palace for a meeting with new French president Francois Hollande earlier this week, will have benefited from the photo opportunity by boosting his statesman credentials.
Downing Street faces awkward questions after Cameron refused to meet with Hollande during the socialist's struggle against Tory ally Nicolas Sarkozy.
A No 10 spokesperson said the prime minister does not "routinely" meet with foreign presidential candidates, adding that the decision is made on a "case-by-case basis".
Romney's visit to Britain will see him take in Friday's opening ceremony at the Olympic Games and a meeting with former prime minister Tony Blair.
His itinerary also includes visits to Israel and Poland, where some expect he will hit out at Russia, which had persuaded the US under Obama to reduce the size of a missile shield based in Poland and Romania protecting Europe.
His trip was controversial before he even boarded the plan, however, after an aide allegedly told the Telegraph of the candidate's belief in the UK and US' shared "Anglo-Saxon heritage". The comment was interpreted as a 'dog-whistle' reference to President Obama's race.