Missile systems will be in place by mid-July
The Ministry of Defence says that similar missile defence systems have been deployed at all recent Olympic Games.
They will be in place by mid-July, along with Royal Navy helicopter carrier HMS Ocean (which will be moored in the River Thames), Royal Air Force Typhoon jets (which will be temporarily stationed at RAF Northolt), and Puma helicopters (at a Territorial Army centre in Ilford).
More top news
Who are the 'Clipperati'?
ITV News London's Chris Paxton is taking part in the round-the world Clipper sailing race. People from across the globe are taking part.
Woolwich heroine 'just talked to a guy who was in need'
A mother who confronted a man suspected of attacking a soldier has exclusively told ITV News she "just talked to a guy who was in need".
Timeline of the attack
How the Woolwich machete attack unfolded, and reactions to the death of a soldier.