From BBC News:
US First Lady Michelle Obama and her children have visited the Houses of Parliament, the BBC understands.
It is thought she visited Big Ben with daughters Sasha and Malia after flying to the UK on Monday morning.
Mrs Obama stayed in Paris on Sunday for sightseeing after her husband, President Barack Obama, returned to the US following an official visit.
Downing Street said that Mrs Obama had not spoken to or met Prime Minister Gordon Brown or his wife.
It would not comment when asked if Number 10 had facilitated the visit, the BBC News Channel's chief political correspondent James Landale said.
Earlier, large numbers of police and security guards had been witnessed underneath Big Ben.
Well they could have paid me a visit!! :P