The number of armed officers in Britain's biggest police force will rise by more than a quarter after the Paris terror attacks.
Currently the Metropolitan Police have around 2,200 trained marksmen and this is set to rise by 600.
Announcing the plan, Scotland Yard chief Sir Bernard Hogan-Howe said: "In the days following Paris I asked my firearms team to increase the number of armed response vehicles available on our streets, which we did. Now I have decided that we take the steps to increase these numbers on a permanent basis.
"To do so, the Met will now start putting plans in place to raise the number of armed officers that we have by 600. This increase will more than double the number of armed response vehicles on our streets and grow a highly trained specialist part of our capability.
"This is because we know that the threat we currently face is likely to be a spontaneous attack that requires a fast response to deal with it.
"This increase has started already and every day we are getting stronger. It will be an expensive option, but is vital to keeping us safe."
Trained firearms officers are all volunteers and force bosses are now holding a recruitment drive to fill the new posts.
Questions were raised over morale among marksmen in the wake of the shooting of 28-year-old Jermaine Blake in north London last month.
Police called for greater legal protection for officers who kill suspects, particularly in light of new counter-terrorism tactics which will see them stepping over casualties to tackle marauding gunmen head on.
Sir Bernard is already meeting armed officers every two weeks in a bid to protect morale.
Speaking on LBC on Wednesday he said: "I've actually met a very large number of our firearms officers after the incident in Haringey to see how they felt, what their complaints might be.
"And I've got the taskforce running now which I'm seeing a group of them every two weeks with things that I'm putting in place to encourage more officers to feel that they've got the confidence that I'm supporting them and in turn the public are supporting them."
Mayor of London Boris Johnson said: "Keeping Londoners safe is my number one priority, and while this city remains one of the safest in the world, the terrible events in Paris last year remind us that we have to be prepared to meet any potential terrorist threat.
"Increasing our armed response capabilities, alongside additional training and support, is absolutely essential, and we welcome the commissioner's announcement today and the funds being made available by the Home Office to support it.
"As a leading world city, London faces unique challenges and a growing population, and it is only right that we ensure the proper level of police protection so we can continue to keep our city safe."
Simon Chesterman, National Police Chiefs' Council lead for armed policing, said: "Following the terrorist attacks in Paris in November 2015, as you would expect we closely examined the incident and our ability to respond to a similar attack in the UK, including the numbers of armed police officers available.
"Individual chief constables and commissioners will take decisions about the number of armed officers required in their force.
"Nationally we are working with all police forces and the armed services to build our capacity at a national level to respond to a well organised, multi-sited terrorist attack in the UK."