Passers-by did double takes as the two politicians strolled Horse Guards Parade, an open stretch behind 10 Downing St., official residence and office of the British prime minister, the Daily Mail reported. Obama's Secret Service detail kept a wary eye on the pair as they chatted.

Obama also held a news conference in front of No. 10, which Brown did not attend. He had some words of comfort for the prime minister, whose poll numbers are even lower than those of U.S. President George Bush.

"Everyone is always more popular before they take charge and once you become responsible you are going to make people unhappy -- it's the nature of politics," he said.

Before breakfast with Brown, Obama spent an hour with former Prime Minister Tony Blair, who came to the Hyatt Regency Churchill. Afterward, Brown went to Westminster to talk to Conservative leader David Cameron in his parliamentary office.

London was the last stop on Obama's tour of the Middle East and Europe, and he headed back to the United States Saturday evening.