Metropolitan Police Commissioner Sir Bernard Hogan-Howe said the body-worn video cameras being trialled would result in speedier justice for victims and help the force be "more accountable".
The commissioner said: "Our experience of using cameras already shows that people are more likely to plead guilty when they know we have captured the incident. That speeds up justice, puts offenders behind bars more quickly and protects potential victims.
"Video captures events in a way that can't be represented on paper in the same detail and it has been shown the mere presence of this type of video can often defuse potentially violent situations without the need for force to be used.
"I believe it will also show our officers at their best, dealing with difficult and dangerous situations every day but it will also provide clearer evidence when it's been alleged that we got things wrong. That has to be in both our own and the public's interest."