London is marking the one year countdown to the Olympic Games with a day of celebrations. British, Prime Minister David Cameron, expressed confidence that London will be a ready host, while IOC President Jacques Rogge, invited athletes from all around the world to visit the city in 2012 and compete.

Hundreds of Britons gathered at Trafalgar Square in London on Wednesday for the one-year countdown to the Summer Olympic Games.

There was a party atmosphere as the crowd listened to speeches from officials.

There was also musical entertainment on hand to keep the fans happy.

Addressing the crowd in the same square where Londoners heard in 2005 that they had won the right to host the Games, Prime Minister David Cameron said the city would be ready.

He said, "It was six years ago in this square that we heard the news that Britain would have the opportunity to host the Olympic Games and six years on, with just one year to go, the sense of excitement is even greater today than it was then."

International Olympic Committee President, Jacques Rogge, formally invited the world to send their athletes to London a year from now.

He said, "I now according to tradition invite the athletes of the world to participate in the games of the 30th Olympiad in London one year from today. Good luck London."

London will be the first city to host the world's biggest sports festival for a third time, after previous games in 1908 and 1948.

Over 15,000 athletes from more than 200 countries will compete at the Olympic and Paralympic Games, with some 10,000 team officials and 20,000 media staff also expected.