Three water cannons bought for the Metropolitan Police service have been sold off without ever being used.

Former London mayor Boris Johnson authorised the purchase of the second hand trucks from Germany, at a cost of more than £300,000, following riots in the capital in summer 2011.

The then Home Secretary, Theresa May, banned them from use and they were subsequently stored at a Met training facility in Mark Lane near Milton Rifle Range in Gravesend.

The cannons, which were bought in 2014, have just been sold for £11,000 to a scrap metal yard in Nottinghamshire.

They cost £322,000 to buy and refit. The price included more than £32,000 to make them comply with emissions regulations, more than £19,000 on repainting them and almost £1,000 was spent on new stereos for each one.

However in 2015, Theresa May banned them from use anywhere in England and Wales.

At the time, she said: "Our police have never and will never routinely carry guns or hide behind military-style equipment."

Johnson’s successor as mayor, Sadiq Khan, pledged to get back as much money as possible by selling them, but almost two years later, they were sold for just £11,025 to the scrap metal firm.

Mr Khan has previously described the move a "another waste of taxpayers" money but added the money raised from the sale will be used to fund youth services in the capital.