The vast security operation to defend Britain's air, land and sea during the Olympic Games came a large step closer to full readiness today.
Surface-to-air missiles were deployed at strategic locations around London, a naval exercise took place off the coast of Dorset and the Navy's largest war ship is moving into place in the Thames. ITV News' UK Editor Keir Simmons reports:
The Ministry of Defence says that the missiles - which include Rapier and smaller High-Velocity Missiles - are being deployed as a "prudent measure" and would only be used as a last resort.
The use of missiles in a densely-populated area would be highly dangerous. Colonel Jon Campbell, commander of the Joint Ground Based Air Defence, said the decision to fire the weapons would be a "political decision" but refused to confirm if the Prime Minister's approval would be needed.
The military has identified six locations around London where missiles could be deployed, although the plan still has to be approved by the Government.
The missiles will form part of an extensive security network that includes Lynx helicopters carrying snipers, Typhoon jets and fast boats on the Thames.
Typhoon jets arrived at RAF Northholt on Wednesday ahead of an eight-day security exercise over the capital. It is the first time fighter aircraft have been stationed at the airbase since the First World War.
HMS Ocean - the Navy's largest war ship - is also en route to Greenwich where it will provide a launch pad for Lynx helicopters and a giant dormitory for some 1,000 soldiers defending the Games.
Earlier, ITV London's Political Correspondent Simon Harris reported from aboard HMS Ocean:
Under the Air Security Plan, a 30-mile zone above the Olympic Park would become a restricted fly zone during the Games.
Observers would be placed at 14 sites to spot potential air threats using binoculars with thermal imaging detecting systems.
Air Vice-Marshal Atha said:
Earlier today, Royal Marine commandos engaged in a security exercise off the coast of Weymouth and Portland in Dorset.
Royal Navy flagship HMS Bulwark is spending four days there to support the exercise, and will be stationed nearby when the county hosts the Olympic sailing events this summer.