He turned to television cameras, smiled, waved and said “hello” before walking into Number 10. Brown greeted him just inside the door.

Pooled television images showed Brown offering Obama a chair on the Downing Street terrace before the pair settled down for two hours of talks.

They later took a stroll in the sunshine around Horse Guards Parade, the vast open space where military reviews, such as Trooping the Color, are often held. Tourists snapped pictures from a distance while security guards walked ahead of the two men.

The walk offered a photo opportunity with a London backdrop for Obama, whose visit to Britain has been decidedly low-key, particularly after the huge crowds he drew earlier in the week in Germany.

Obama later said he had also wanted to take a walk through St. James’ Park, but security guards pulled him and Brown back. The park is near Buckingham Palace, home of Queen Elizabeth II.

Obama stressed the importance of the bond between the two nations.

“We’ve been through two world wars together. We speak a common language. We share a belief in rule of law and due process,” he said “We just like the people. There is a deep and abiding affection for the British people in America and a fascination with all things British that’s not going to go away any time soon.”

The Illinois senator also offered reassurance to Brown, whose plummeting popularity took another hit this week when he lost a parliamentary by-election in a Scottish seat long held by the governing Labour Party. But Obama pointedly said Brown didn’t need his political advice.

“You’re always more popular before you’re actually in charge,” Obama said. “Once you’re responsible, then you’re going to make some people unhappy.”

From 10 Downing Street, Obama traveled a short distance to meet with David Cameron, leader of the opposition party. The two men sat in comfortable chairs in an alcove for their discussions.

Earlier, he met with former Prime Minister Tony Blair, who is now a Middle East envoy. The meeting lasted for just over an hour.

Obama is winding up an election-season trip, financed by his campaign. Part of his goal for the trip through Afghanistan, the Mideast and Europe has been to allow him to make his debut on an international stage in the hopes of reassuring skeptical voters in the United States about his readiness for the presidency.

On Friday, he met for more than an hour with French President Nicolas Sarkozy at the Elysee Palace in Paris.