LONDON -- It was a show of force on Britain's streets Wednesday.
Soldiers joined police on patrols to protect potential targets including Buckingham Palace and Parliament --.
Up to 3,800 troops can be mobilized; About 1,000 were deployed Wednesday.
Londoner Peter Atherton says relying on the military makes sense.
"We have a limited number of armed policemen in the UK, so they need to be now doing other things than just guarding government buildings," he said.
The last time the military was mobilized like this was in 2003, when tanks and troops were sent around London and to Heathrow Airport following a plot to bring down an airliner with a surface-to-air missile.
Wednesday, to free up police, Parliament was closed to the public and the ceremonial changing of the guards was cancelled at Buckingham Palace.
The extra security reassured Michelle Calvert from Manchester.
"That's the British way isn't it? We just get on with things don't we? Carry on," she said.
Police say another attack may be "imminent." That means the public will need to get used to seeing the military in their cities.