London2012 chairman Sebastian Coe delivers his speech during the closing ceremony of the London 2012 Olympic Games at the Olympic stadium August 12, 2012. REUTERS/Jeff J Mitchell/Pool (BRITAIN - Tags: SPORT OLYMPICS)

London2012 chairman Sebastian Coe (R), Catherine, Duchess of Cambridge (2nd R), and Prince Harry (3rd R) stand for the national anthem during the closing ceremony of the London 2012 Olympic Games at the Olympic Stadium August 12, 2012. REUTERS/John Stillwell/pool (BRITAIN - Tags: SPORT OLYMPICS ROYALS)

Britain's Prime Minister David Cameron (L) speaks with London2012 chairman Sebastian Coe (2nd R), as Catherine, Duchess of Cambridge (2nd L) and Samantha Cameron listen during the closing ceremony of the London 2012 Olympic Games at the Olympic Stadium August 12, 2012. REUTERS/John Stillwell/pool (BRITAIN - Tags: SPORT OLYMPICS ROYALS POLITICS ENTERTAINMENT)

Britain's Prime Minister David Cameron (R) speaks as London2012 chairman Sebastian Coe watches during a news conference in the garden of number 10 Downing Street in London August 12, 2012. Coe will serve as Cameron's Olympic legacy ambassador after the Games finish on Sunday, the British government said. REUTERS/Dan Kitwood/Pool (BRITAIN - Tags: POLITICS SPORT OLYMPICS)

Britain's Prime Minister David Cameron (R) speaks as London2012 chairman Sebastian Coe watches during a news conference in the garden of number 10 Downing Street in London August 12, 2012. Coe will serve as Cameron's Olympic legacy ambassador after the Games finish on Sunday, the British government said. REUTERS/Dan Kitwood/Pool (BRITAIN - Tags: POLITICS SPORT OLYMPICS)

OLYMPICS/LONDON2012 - Preview graphic of the London 2012 Olympic Games locating sport venues. Includes 3-D diagram of the London Olympic Stadium. RNGS (SIN05)

OLYMPICS/LONDON2012 - Preview graphic of the London 2012 Olympic Games locating sport venues. Includes 3-D diagram of the London Olympic Stadium. RNGS (SIN05)