As a lesson in good natured statesmanship - if not to say simple manners - it was a masterclass.

For Michelle Obama cast aside stuffy protocol to join in the fun and games to celebrate today’s opening of the Olympic games with more than 1,000 children.

The First Lady met the children - most of them from U.S. military families - in the grounds of Winfield House, the official residence of the U.S. ambassador in London.

She was joined by David Beckham and Olympic gold-medal sprinter Carl Lewis who signed autographs.

She said: “I’m so excited,” after jogging to the stage as a marching band played the University of Florida fight song.

“I am thrilled to be here on London for the 2012 Olympic games. I am proud to be leading the U.S. delegation to the opening ceremony.”

Mrs Obama, who later tried out sports including tug-of-war and football alongside the children, offered a tribute to military families who had been invited to take part in the event.

“The military families who are joining us from U.S. bases that are stationed here in the U.K., we are so grateful for your service because you all sacrifice so much - you as kids, your mums, your dads,” said the First Lady. “You sacrifice so much for this country and we are so very proud of you.”

It was a somewhat different story from another American visitor, presidential candidate Mitt Romney, who was forced to apologise for his comments about London’s readiness for the Games.

The gaffe-prone Republican told US channel NBC’s Today Show: “After being here a couple of days it looks to me like London is ready”.

His comments followed criticism from both David Cameron and Culture Secretary Jeremy Hunt as well as worldwide condemnation from Twitter users who got #romneyshambles trending on the microblogging site.

Even London Mayor Boris Johnson got in on the act, persuading audiences at a pre-Olympic party in Hyde Park to chant Mr Obama’s election slogan.

Rousing the crowd of at least 60,000 he told them: “There’s a guy called Mitt Romney who wants to know whether we’re ready. Are we ready? Are we ready? Yes, we are.”