The Armed Forces are drafting emergency plans to provide 3,500 extra troops for the Olympics because of a humiliating security blunder.
Theresa May has been forced to plead with the Ministry of Defence to release thousands more service personnel during London 2012 as guards.
The Home Secretary was forced into the last-ditch move a fortnight before the Games because security firm G4S has been unable to guarantee it will be able to supply the 10,000 guards it agreed to deliver.
Talks began with the MoD over whether it could fill the gap after the company wavered on its commitments.
The development could see troops deployed to check tickets, search spectators’ bags and prevent outbreaks of trouble at the Olympic Park in Stratford, east London.
A Whitehall source said: ‘The army will provide an insurance policy.’
The Armed Forces are already providing up to 13,500 personnel for the Games.
Under the contingency plans, this could reach 16,500 – 7,000 more than are fighting in Afghanistan.
Originally, Locog contracted G4S to provide just 2,000 security guards of the 10,000 it thought it would require.
But in December the firm agreed to supply 10,000 of the new total of 23,700 under a new contract reported to be worth £284million.