So far, 339 officers who retired in the last five years have applied to return to the Met Police.
The first have already started training to prepare them for returning to duty on Monday.
More than 30 other former officers have applied to work as special constables.
Meanwhile, another 307 who retired more than five years ago have also volunteered to help the force.
Metropolitan Police Commissioner Dame Cressida Dick said she was “incredibly grateful”.
It comes as police force chiefs told the Commons Home Affairs Committee that around 13 per cent of police officers across the UK were currently off work.
MPs were also told on Monday officers may be able to get tests to check if they have coronavirus by the end of the month.
Chief Superintendent Paul Griffiths, president of the Police Superintendents Association of England and Wales, said: "Obviously the key workers that they're (the Government) focusing on at the moment is National Health Service and we recognise the importance for both national health colleagues and also social care.
"But we also are key workers in this system and we're very keen to make sure that we have a position within the testing regime and prioritisation.
Mr Griffiths said: "We are obviously experiencing an absence rate.
"The absence rate is approximately 13% across the whole of the national establishment and that includes police officers and staff.
"Those will be sick, some of those will be self-isolating because of symptoms and some of them will have caring responsibilities.
"Most of them are trying as best as possible to see whether they can work at home, which gives you an idea of the solidarity that continues across the police service in trying to do their very best in extreme circumstances."
He said no forces had so far raised their absence rate as a "risk in terms of service provision" and the numbers seemed to be "plateauing off".
But he added: "We are acutely aware that this could change at any point and quite frankly we don't know what the impact will be if this disease continues to spread particularly into members of the police family."
Simon Kempton, from the Police Federation of England and Wales, said that some forensic laboratories could be re-purposed to process tests.
But he said: "Even then if we are able to do that, there are going to be some really difficult decisions about which officers get the tests and which don't; or which get them first and which have to wait."
When asked about a timetable for testing, he added: "My expectation is that we will begin to see those tests coming online middle to the end of April."
Mr Kempton said something had "gone wrong" in the supply chain of personal protective equipment (PPE) for officers.
While a "huge amount" of PPE has been ordered by forces, it is not always getting to frontline staff.
He was forced to go out to arrest a suspect thought to have Covid-19 without the equipment, MPs heard.
Some forces have set up dedicated "Covid cars" that carry PPE, but there are others where officers are having to share the kit.