The claim: The Metropolitan Police is facing cuts of £400m by 2021.

Reality Check verdict: The Metropolitan Police's budget will be flat in cash terms, so there is not going to be a cut in that sense, but the Mayor of London's team calculates that rising costs will mean savings of £400m will need to be found between 2017-18 and 2020-21.

Former Metropolitan Police Commissioner Lord Blair told Tuesday's Today Programme that police cuts need to be reconsidered.

Later, a spokesperson for the Mayor of London said: "It is simply not true to say that the Met's budget has been protected... the Met now has to find a further £400m."

But on Wednesday's programme, First Secretary of State Damian Green said: "There are no police cuts. We have protected police budgets in this parliament."

So who is right?

The Met is getting the same amount of cash each year, so it is not being cut in that sense, but its costs are rising.

Reality Check has looked at the overall funding of policing in England and Wales before. Overall the police budget in England and Wales has been protected in real terms, but not every individual force will feel the benefit because the money is being targeted at specialist areas of policing. The relatively small funding boost comes off the back of five years of deep cuts.

The calculation that rising costs will mean that the Met needs to find savings of more than £400m by 2020-21 comes from the Mayor of London's Office for Policing and Crime (MOPAC) budget submission from December last year.

It says the extra costs cover "a range of items" including:

Rises in pay and general inflation

Pension costs

Spending on firearms

Investment in modern IT and mobility.

The Home Office said: "Her Majesty's Inspectorate of Constabulary has been clear that there remain significant efficiencies in policing to be delivered from digitisation, collaboration and improving workforce capability," so it seems confident that efficiencies can be used to cover the extra money needed.

Speaking to the London Assembly on Wednesday, Metropolitan Police Commissioner Cressida Dick outlined some of the areas where savings could be made and said that despite those: "If we don't get any further money it will be very difficult for us to provide some of the services we currently provide."

Deputy Commissioner Craig Mackey said: "It's like saying you take home £1000 a month and in four years time you'll still be taking home £1000 a month. Will you still feel as well off? No you won't."

Image copyright Getty Images Image caption There is increased security in London

There are two other issues surrounding the Met's funding. The first is that the government has been considering a review of the police funding formula, which dictates how money is shared out between police forces.

There was concern that this might leave the Met with less money. There were reports on Tuesday that those plans had been scrapped, but the Home Office has stressed no decisions have yet been taken on that.

The £400m calculation was based on the old funding formula, so any changes to funding would be on top of that.

The other issue is that the Met gets a National, International and Capital City (NICC) grant, to cover the extra work it needs to do as a result of operating in a major city.

The tightened security in London means it is likely to have to spend more on these sorts of functions, but MOPAC says there is a £170m a year shortfall between what the Met is currently spending on such functions and how much it receives from the Home Office.

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