The US First Lady was accompanied in central London by her daughters, Malia, 16, and 14-year-old Sasha and her mother, Marian Robinson.
She is in the UK to help highlight her campaign to get more of the world's poorest girls get educated and make it 'an urgent economic issue'.
It is something she had planned to discuss with the Camerons today over afternoon tea, after arriving at Downing Street at about 5pm.
She hoped to appeal to him to help adolescent girls worldwide attend school and discuss joint work between the countries to boost education.
