Michelle gets jitters about the Queen

Barack Obama told of his wife's trepidation as he described his own feelings about seeing the Queen. "I'm very much looking forward to meeting her for the first time," he said.

"Michelle has been really thinking that through because in the imagination of people throughout America what the Queen stands for, her decency, her civility, what she represents, is very important," he told a press conference at the Foreign Office."

American journalists understood the comments to be a reference to the controversy over the First Lady's clothes.

When Mrs Obama arrived at Downing Street today for breakfast with the Browns, her shoulders were covered by a cream sequin cardigan. However, she has come under fire in America after she wore a navy sleeveless dress for her first official White House photograph.

Fashion experts branded it too informal and a debate has erupted in the US over what she will wear to see the Queen at Buckingham Palace later today.

The palace said there was no etiquette for what the president's wife should wear, adding that general advice would be given if requested but not down to details such as length of sleeves.
"All guests to Buckingham Palace can really wear what they deem to be acceptable," said a Palace spokeswoman.

While their husbands were in discussions, the First Lady and the Prime Minister's wife Sarah Brown visited Maggie's Centre for cancer care at Charing Cross Hospital, which was marking its first birthday.

Mrs Obama had tea with patients and staff at the centre, of which Mrs Brown is patron. A crowd gathered outside, eager for a glimpse, while nurses leaned out of windows. When she emerged after almost an hour, Mrs Obama was greeted by cheers and screams and shouts of "Obama, Obama".

During their visit, Mrs Obama and Mrs Brown sat in on a make-up session for women suffering from cancer and even shared gardening tips, with Mrs Obama telling staff and patients how she planned a beehive on the White House lawn.

Mrs Obama then joined members of the centre in a traditional British cup of tea. She described Maggie's as "amazing", saying: "This is pretty incredible. This is pretty amazing, it's an oasis — an oasis that's necessary for people who are struggling."

Among those she met was 32-year-old Namina Turay, who was diagnosed with breast cancer in 2007 but is now in remission. Ms Turay said Mrs Obama had been "warm and friendly". She said: "It's her first official visit and this is a great honour. It's such a privilege, she's so natural and really easy to talk to."

Tonight, while the G20 leaders have a working dinner, Mrs Brown and Mrs Obama will meet again for a "night in" in Downing Street, with dinners for both cooked by Jamie Oliver and staff from his Fifteen restaurant.

They will be joined by British women from the worlds of showbusiness and sport, including Olympic gold medallist Dame Kelly Holmes, author J.K Rowling, internet entrepreneur Martha Lane Fox and broadcaster Emma Freud.