Firearms officers working in the capital will be given head-mounted cameras to boost transparency, more than three years after the plans were first mooted.
The Metropolitan Police said officers working for armed response units will have the devices attached to baseball caps and ballistic helmets.
Cameras have already been given to 17,500 officers in the country's largest police force, with the latest tranche seeing 1,000 members of Firearms Command getting the devices.
The plans were first suggested by previous Met commissioner Sir Bernard Hogan-Howe in 2014 in the wake of the death of 29-year-old Mark Duggan.
Sir Bernard said giving firearms officers cameras would result in speedier justice for victims and help the force "be more accountable" in the wake of the death which sparked riots in 2011.
Commander Matt Twist, in charge of the Firearms Command, said: "Officers who carry an overt firearm as part of their role very much welcome the use of Body Worn Video.
"It provides a documented and accurate account of the threats officers face and the split second decisions they make.
"The cameras also offer greater transparency for those in front of the camera as well as those behind it."
Only those officers who carry a firearm overtly will be given a camera, while other units including Mounted Branch, Parliamentary and Diplomatic Protection and Specialist Crime Units to be given the devices by October.
London mayor Sadiq Khan said the technology "will make a real difference to those carrying firearms"
He said: "As we complete the London-wide rollout, the cameras will also provide our officers with confidence in the transparency of their actions, as they continue their great work on the front line fighting crime and keeping our city safe."