Scotland Yard is to train a squad of riot police as firearms officers to act as a reserve force to cope with a Paris-style terror attack.
Around 200 officers from the Territorial Support Group are to get firearms training to create a back-up squad in case of a massive terrorist assault on London.
The officers will not carry weapons in their normal public order duties or while on patrol in London, but will be called on if all the Met’s firearms capability is committed to dealing with a co-ordinated multiple attack.
The TSG group will be part of a “second wave” of armed officers sent in to tackle fanatics.
It will form part of the extra 600 firearms officers announced by Met Commissioner Sir Bernard Hogan-Howe in January after the Paris atrocities last November.
About 400 of these will be deployed into armed response vehicles, or Trojans, dramatically increasing the number of units on patrol across London.
Scotland Yard is spending around £25 million on equipping the units, which patrol in three-man teams, carrying Sig Sauer semi-automatic carbine rifles and Glock pistols. They routinely patrol boroughs with the highest levels of gun crime.
Last year it was revealed firearms officers are being told to walk over casualties and go forward to confront terrorists if there is an attack.
The TSG is in the front line of policing violent protests and disorder in the capital and carries out routine patrols of crime hotspots. The squad has faced criticism over its policing methods in the past but the number of complaints has fallen in recent years.
The unit came under particular criticism after the death of newspaper seller Ian Tomlinson in 2009 during a protest. Images emerged of Tomlinson being struck by TSG officer Simon Harwood, who was later found not guilty of manslaughter but sacked for gross misconduct.
Insiders say the TSG officers will be recalled to be issued with weapons in a terror attack.
Sir Bernard told a recent London Assembly meeting they could be used to provide a “surge capacity”.
A Met spokeswoman said: “There is no change in the plan to raise the number of armed officers by about 600. Of those, 400 will be officers in the Force Firearms Unit (SCO19) and the remaining number of officers within other roles across the Met, and one of those options includes officers from the TSG.”