Prime Minister David Cameron today met the Republican candidate for US president Mitt Romney during his campaigning and fundraising visit to London.
The meeting in 10 Downing Street came after Mr Romney appeared to question Britain's readiness to host the Olympic Games, telling a US television station there were "disconcerting" signs and it was "hard to know just how well it will turn out".
He today told the Prime Minister he was inspired by the enthusiasm of the British people who have lined the route of the torch relay ahead of tomorrow's opening ceremony.
Mr Cameron and Mr Romney shook hands warmly as they began their talks in the White Room of Number 10 which has a view on to the stadium, erected in Horse Guards Parade, for the Olympics beach volleyball.
Mr Cameron said: "I've been over to the park today, it is looking good, I've been at every stage and you can never quite believe it's going to make it, so when it does, it's great."
The Prime Minister said the Olympic torch would be coming to Downing Street later today, but added: "Politicians aren't allowed to touch it, quite rightly, the torch is about the people and the athletes."
Mr Cameron explained that many of the torch bearers were chosen as inspiring figures in their communities, and Mr Romney responded: "I was watching last night the torch relay coming across Great Britain and the stories about that and the enthusiasm attached."
Recalling his own stint as chief executive of the Salt Lake City Winter Olympics in 2002, he said: "For me, the torch relay was one of those moments that brought people together and I will not forget it.
"The Games unified the community in a way people hadn't expected. It brought together disparate voices and ushered in a moment of unity."
Mr Romney's visit - during which he was also meeting Deputy Prime Minister Nick Clegg, Chancellor George Osborne, former PM Tony Blair and Labour leader Ed Miliband - is an important opportunity for the presidential candidate to demonstrate his grasp of foreign affairs and ability to represent the US overseas.
He is also visiting Israel and Poland as part of the same tour.
His campaign team has already been forced to distance itself from a briefing on US-UK relations after an unnamed adviser reportedly told the Daily Telegraph that he had a better understanding of the two countries' "Anglo-Saxon heritage" than his Democrat rival, incumbent president Barack Obama, who is of African-American descent.
US vice president Joe Biden called the remarks "disturbing".
Mr Cameron has faced questions over his willingness to have talks with an election candidate - particularly after he refused to meet Francois Hollande, the Socialist challenger and eventual victor in the French presidential election, earlier this year.
At the time, Mr Cameron's official spokesman said the "usual procedure" was for the Prime Minister not to meet candidates in elections in foreign countries.
Mr Romney is trailing Mr Obama by a narrow margin in the latest polls.
After speaking at an investment conference at Lancaster House, London Mayor Boris Johnson dismissed the suggestion that the capital was unprepared for the Games.
"London is as ready as any city has been in the history of the Olympic Games," he told reporters.
"I'm worried that I haven't got enough to worry about."
Mr Johnson also played down an incident where the North Korean football team was welcomed on to the pitch with a South Korea flag.
"The North Korean delegation is now content," he said.
Meeting Mr Miliband in his Westminster office, Mr Romney said he recognised the "unique relationship" which exists between Britain and the United States.
He also praised the efforts of Britain's Armed Forces in the "joint effort" in Afghanistan, saying "the people of Great Britain have sacrificed enormously in helping bring peace to that nation".
There was some Twitter speculation that he might have momentarily forgotten Mr Miliband's name, after he addressed him as "Mr Leader".
Replying to Mr Miliband in front of the Press, Mr Romney said: "Like you, Mr Leader, I look forward to our conversations this morning... and recognise, of course, the unique relationship that exists between our nations, our commitment to common values, our commitment to peace in the world and our desire to see a stronger and growing economy."
Mr Miliband greeted Mr Romney with a handshake as the pair held a brief question-and-answer session with waiting British and American media, before meeting in private for talks on a range of issues.
Asked about Olympic security issues and last night's error over the North Korean team flag, Mr Romney replied: "It is impossible for absolutely no mistakes to occur.
"Of course there will be errors from time to time, but those are all overshadowed by the extraordinary demonstrations of courage, character and determination by the athletes.
"The Games are, after all, about the athletes, the volunteers and the people of the community who come together to celebrate those athletes.
"As soon as the Games begin, we all forget the organisers and focus on the athletes."
Asked if he was excited about the London Games, Mr Romney replied: "Absolutely, The weather could not be better - fortunately the sunshine is out, the warmth is here - the athletes have arrived and the Torch is about to come into London, and I know the spirit of the people in this community will welcome the athletes of the world.
"My experience is that this event will change the hearts of many, many people. Anyone who gets the opportunity to touch the Olympics will long remember the kind of service they can provide to the people of the world and remember the heroics of the athletes themselves."
The Labour leader said he was looking forward to discussions with Mr Romney on a range of issues, including the international economy, Syria and events in the eurozone, as well as "our shared commitment to the Boston Red Sox" baseball team.
Mr Miliband said: "There is a special relationship between Britain and the United States, expressed in our shared history and also in the current commitments that we have together.
"I welcome this meeting because I think we come from different parties and also different viewpoints on some issues, but I think it's incredibly important that leaders work together and that we respect the electorates in each of our countries."
In an interview recorded before his meeting with Mr Romney, Mr Blair refused to be drawn on who he wanted to win the election, but said the UK would have to work with whoever emerged as the new president.
Mr Blair told CNN: "However special the relationship, you don't decide our elections and we don't decide yours.
"It is important for the British to work with whoever comes out of the presidential process.
"I have worked closely with President Obama over these last few years on the Middle East and I have a great admiration and work well with him."
Mr Blair said the transatlantic relationship between the US and UK is "still strong, because of tied history, shared values and shared purpose".
He added: "It's a very strong and good relationship and always should be.
"People used to say to me 'You get on with Bill Clinton and you get on with George Bush' and I used to say I like them both very much in different ways, but it is partly the job of the British Prime Minister to have that relationship with the American President.2
Following the meeting, Mr Blair's spokesman said: "Ahead of the Governor's visit to the Middle East, they discussed the Middle East peace process, the situation in Syria, Iran and the wider region.
"The meeting then covered the economic challenges facing both Europe and the US. On the eve of the Olympic Games, the Governor and Quartet Representative also discussed their medal hopes for the US and British Olympic teams."
Speaking to NBC News, Mr Romney appeared less than confident that the London Games would be a success.
"It's hard to know just how well it will turn out," he said. "There are a few things that were disconcerting.
"The stories about the private security firm not having enough people, the supposed strike of the immigration and Customs officials - that obviously is not something which is encouraging."
He also appeared to question Britain's enthusiasm for the Games: "Do they come together and celebrate the Olympic moment? That's something which we only find out once the Games actually begin."
Addressing the Press after he emerged from Number 10, Mr Romney revealed that he had spoken with MI6 chief Sir John Sawers today and had discussed a number of international issues, including Iran, Syria, Afghanistan, Libya, Egypt, Tunisia and Pakistan, with the Prime Minister.
But he refused to be drawn on the content of their discussions.
Asked whether his comments to NBC meant he was concerned about the smooth running of the London Olympics, Mr Romney said: "I am very delighted with the prospects of a highly successful Olympic Games. What I have seen shows imagination and forethought and a lot of organisation.
"I expect the Games to be highly successful."
Mr Romney said that, watching coverage of the Olympic Torch Relay: "I saw the response of tens of thousands, millions of people across Great Britain. The enthusiasm for the spirit of the Olympics and the symbolism of the torch, which represents hope and opportunity was heartening to me and heartening, I'm sure, to all those who have had the chance to touch the torch.
"I also applaud the work of the organising committee in bringing the Olympic experience right into the heart of London.
"To look out of the back side of 10 Downing Street and see a venue having been constructed and knowing that athletes will be carrying out their competition almost in the backyard of the Prime Minister is really quite an accomplishment on the part of those who wanted to make sure that the Olympics was not something held far off where the people can't enjoy, but something held right in London itself.
"This is an indication of a community that will share in the Olympic experience, be inspired and uplifted by it."
He added: "My experience as an Olympic organiser is that there are always a few very small things that end up going not quite right in the first day or so, and these are ironed out and, when the Games begin and the athletes take over, all the mistakes the organisers make - and I made a few - are overwhelmed by the many things the athletes carry out that capture the spirit of the Games.
"I don't know of any Olympics that has been able to be run without any mistakes whatsoever, but they are small and I was encouraged to see that something that could have represented a real challenge, which was the immigration and Customs officers on duty, was something that was resolved and people are all pulling together."
Mr Romney said his meetings today were "enlightening and instructive".
And he added: "I also feel, as Americans do across our nation, a special relationship with the nation of Great Britain and with the people here.
"Obviously, our appreciation for the contribution of British soldiers, fighting side by side with those of the coalition and those of our nation in Afghanistan and elsewhere in the last years is something which is important to us and that we recognise as a contribution that has bettered the world."