Some 600 extra specialist officers will be on duty
Increased numbers of British armed officers are to mount patrols across London, including at major landmarks, in the wake of the deadly terror attacks in Europe.
Revealing plans for the heightened visible presence on the streets of the UK capital, Met Police chief Bernard Hogan-Howe said it would be "foolish to ignore" the recent atrocities on the continent.
The 600 extra specialist officers will be there to "confront terrorists" and are "prepared to deal with the worst situations", he insisted.
With the terror threat level in the UK ranked as severe, Mr Hogan-Howe stressed the need for vigilance with an attack "highly likely".
He was speaking after warning that a terror attack in Britain was a case of "when, not if".
Mr Hogan-Howe said: "We've seen attacks in Germany, we've seen attacks in France and Belgium and I think we'd be foolish to ignore that."
"So it's important we get officers out there with firearms to respond where necessary but they are the same officers they were before, they're part of British policing."
"I want them to be friendly; I want them to approach the public and to be approachable to the public. I want the public to be able to go up and talk to these officers and that's part of their briefing."
"They've not changed but they are ready for the sorts of things we've seen throughout the rest of Europe."
London Mayor Sadiq Khan said: "The police work incredibly hard, but they cannot do it by themselves. If you know anything that might be going on in your neighbourhood, if you're suspicious of a member of your family, a neighbour, somebody who works with you report it to the authorities."
"Of course we will do our bit to make sure we have the resources they need but they more importantly need our intelligence from members of the public so please feel free to report things to members of the police."
But the main police union has warned that it could be two years before 1,500 extra firearms officers due to be trained by police forces throughout England and Wales are operational.
Police Federation of England and Wales chairman Steve White said the "best case scenario" would be 24 months to get the additional marksmen in place.