More than four billion people worldwide are expected to tune in to watch the opening and closing ceremonies for the London Olympics - worth up to STG5 billion ($A7.7 billion) in advertising terms, organisers say.

About 20,000 people from across the UK will perform in the four ceremonies next year.

Organisers have so far remained tight-lipped about which big acts will feature in the ceremonies at the start and end of the Olympic and Paralympic Games - rumours include performances from Take That, the Spice Girls and even Beatles legends Sir Paul McCartney and Ringo Starr, but nothing has been announced officially.

The London Organising Committee of the Olympic and Paralympic Games (LOCOG) says more than 10,000 hopefuls turned up for a first round of auditions for volunteer performers at the ceremonies.

The ceremonies are predicted to be viewed by a worldwide TV audience of four billion people in more than 200 countries.

In advertising terms, the equivalent airtime value is expected to be worth between STG2 billion and STG5 billion.

Sir Martin Sorrell, head of advertising giant WPP, said: "The London 2012 opening and closing ceremonies will be four of the biggest moments in TV history, broadcast in over 200 countries to an audience of four billion people.

"The equivalent advertising value that will deliver for the UK could be up to STG5 billion, however with regards to perception of London and the UK and a tourism legacy you could say that they will be priceless."

A team of leading British creative talent has been put in place to lead the direction of the Olympic and Paralympic ceremonies.

In May 2010 filmmaker and producer Danny Boyle was appointed as artistic director for the opening ceremony, while director Stephen Daldry, designer Mark Fisher, Hamish Hamilton - best known for his direction of live TV events - and Catherine Ugwu, producer of the 2002 Manchester Commonwealth Games, were appointed as executive producers across all four ceremonies.

And in February this year, Take That's creative director Kim Gavin was appointed artistic director for the closing ceremonies of both the Olympic and Paralympic Games.

The closing ceremonies team also includes multi-award-winning stage and costume designer Es Devlin and Bond film composer and record producer David Arnold.

In June 2011, Jenny Sealey and Bradley Hemmings were appointed as artistic directors of the opening ceremony of the London 2012 Paralympic Games.

Music directors for the opening ceremony are expected to be announced shortly.

Jeremy Hunt, Secretary of State for Culture, Olympics, Media and Sport, said: "I am incredibly excited about Danny Boyle's amazing plans for London's opening ceremony.

"Four billion people around the world will be absolutely wowed by what they will see by the Olympic and Paralympic opening and closing ceremonies.

"The ceremonies will be the most fantastic advert for everything that is great about our country."

PA