Helicopters will be based on HMS Ocean, the Navy’s largest ship, anchored in the Thames off Greenwich, while the jets will be located outside London but will be able to reach the Olympic site in minutes.

Typhoon planes that were used against Colonel Gaddafi’s regime in Lybia will be moved to RAF Northolt, north-west London from Scotland and Lincolnshire.

Defence Secretary Philip Hammond said the Games was “the biggest security challenge this country has faced for decades”.

He added that military deployment during the Olympics has been routine since the 1996 Atlanta Olympics.

He said: “This defence contribution is on a similar scale to that deployed at other recent Olympic Games and will contribute to ensuring a safe, secure and enjoyable 2012 Olympics.”

“Defence will continue to be able to support current and contingent operations during the games and my priority will remain the troops we have deployed on operations, including in Afghanistan, before, during and after the Olympics.”

There will be around 7,500 members of the armed forces working as security guards at the venues. There will be a further 5,000 supporting the police and 1,000 giving logistical support.

Marines who fought in Libya will also be based on HMS Ocean and will patrol along the Thames to deal with any threats.

Special forces will be on high alert and military explosive disposal teams plus units with dogs that can search vehicles and buildings will be on hand.

Security allocation for the games has been raised by £271 million to £553 million after the number of security guards was more than doubled to 23,700.

Organisers said international uncertainty made the increase of troops necessary.