A body worn video camera on the uniform of a police officer seriously injured in a "shocking and cowardly" attack in Brentford is missing.
Officers in Hounslow are appealing to anyone who may have found the equipment following the assault, in which a 32-year-old cop was left with a broken nose and fractured jaw.
Anyone who has found the device is urged to return it to a local police station.
The borough's police took to the streets with the new cameras just a few days before on Wednesday, June 7.
Appeals continue for witnesses and information surrounding the assault in Boston Manor Road at around 9.35pm on Saturday (June 10).
There were many people in the area due to a music event taking place close by, police said.
Detective Chief Inspector Helen Flanagan of Hounslow CID said: "The body worn video camera is a new piece of kit that officers on our borough are wearing.
"They are encrypted devices the footage cannot be accessed by anyone other than our officers.
"However, we are obviously keen for the camera to be returned to us and I would ask anyone who has seen it, or has it in their possession, to drop it off at their local police station.
"This was a shocking and cowardly attack on a police officer going about his duty.
"There were large numbers of people in Boston Manor Road as there was a music event taking place nearby and I would appeal to anyone who saw this incident to contact police immediately."
Two officers drove to the scene after police were called to reports of an assault, the Met said.
On arrival, a member of the public pointed out a man they believed was involved in the fight who was running off down the street.
Police pursued the man and told him to stop, but he did not.
Both officers got out of their car and attempted to detain the man.
However, in this time a crowd of people had gathered and began acting in a hostile manners towards the police.
One man in the crowd kicked one of the officers in the face, breaking his nose and fracturing his jaw.
Meanwhile the other officer used CS spray to disperse the crowd.
Support was called to the scene.
The injured officer was taken to the West Middlesex Hospital for treatment, and has since been discharged.
Anyone with information on the incident and the location of the camera is asked to call Hounslow CID on 020 8247 6224 or 6299 or call Crimestoppers anonymously on 0800 555 111.
The police can be contacted via Twitter by using @MetCC.
A 21-year-old man detained was arrested for obstructing police and taken to a west London police station.
He has been bailed pending further enquiries to a date in early July.
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