London 2012: 4 billion to watch ceremonies

London 2012 organizers say more than 4 billion people will watch the opening and closing ceremonies for next year's Olympics and Paralympics.

About 20,000 people will perform in the four ceremonies but the local organizing committee has yet to announce the headline performers.

British media have speculated that Paul McCartney and Ringo Starr may perform.

Advertising executive Martin Sorrell says the huge audience means the ceremonies are worth $3.2 billion in advertising to Britain.

Sorrell adds that "with regards to perception of London and the UK and a tourism legacy, you could say that they will be priceless."