Next month the Met will be piloting 500 body-worn cameras with police officers on the beat in nine London boroughs.

If successful, it will be rolled out across Britain's biggest police force .

BBC London's home affairs correspondent Guy Smith went to Rialto in Southern California where they have carried out a pioneering experiment with officers wearing the body cameras for over a year.

The use of force there fell 60% and complaints against officers dropped by more than 80%.

Rialto Police Department's Chief Tony Farrar, Sgt Josh Lindsay and Corporal Gary Cunningham as well as Peter Bibring of American Civil Liberties Union talk about the scheme.