There were squeals, high-fives and tears. Michelle Obama electrified a North London school in a surprise visit during which she told children to remember that “being smart is cooler than anything in the world”.

America’s First Lady appeared at times overwhelmed by the reaction to her visit to the Elizabeth Garrett Anderson School in Islington.

In remarks to 100 teenage girls who had no idea that she was coming, Mrs Obama said that education, rather than their background, counted the most in life.

“If you want to know the reason why I am standing here, it’s because of education,” she told them.

“I never cut class. I loved getting As, I liked being smart. I liked being on time. I thought being smart is cooler than anything in the world. You, too, with these values, can control your own destiny. You, too, can pave the way.” She urged them to believe in their dreams.

“For nothing in my life ever would have predicted that I would be standing here as the first African-American First Lady. I was not raised with wealth or resources or any social standing to speak of. I was raised on the South Side of Chicago — that’s the real part of Chicago.”

Afterwards, she let slip that “I do hugs” and was immediately mobbed by dozens of girls as she leant over the stage to greet as many as possible. Throughout the visit the girls yelled: “We love you”.

Mrs Obama, on her first official visit as First Lady, paid tribute to her British hosts, saying that the country was the home of the “most extraordinary women”, including the Queen and Maggie Darling, the wife of the Chancellor, whom she called a “true firebrand”. She described Sarah Brown as a “phenomenal woman who has been charming and delightful”.

On Wednesday night Mrs Obama and her husband made a special point of seeking out the dozen or so Downing Street custodians and staff who had stayed on hand to help, thanking them all, and the President saying that he could understand how tired they must have been feeling.

Mrs Brown, who has been hosting the leaders’ wives for the past 48 hours, spent yesterday morning at the Royal Opera House with other spouses.

Afterwards, Svetlana Medvedev, the wife of the Russian President, said: “We are proud to be here with the men who are making these decisions which mean so much to the people in our countries. Now I think if we all clap loud enough, they will hear us and maybe that will inspire them to get the agreement.”

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