CCTV is mandatory in all English slaughterhouses. Vets, of course are always on the premises but they cannot be everywhere at once. It was clear to animal rights activists that ill-treatment was inevitably widespread.
CCTV is not mandatory in English hospitals, care homes or anywhere else, except for police stations.
It produced a rapid drop in the number of people who "fell down the steps on the way to the cell". But it proved useful to police officers, too, because it showed them innocent of many false accusations. It also provided evidence for any later legal procedures.
Police were hostile at first, but quickly became enthusiasts, and also adopted shoulder-worn cameras for their own protection.
Use independently monitored, (randomly requested) footage of CCTV (from overt plus from randomly moved hidden cameras) and body-cams in all settings where abuse is possible.
The supposed 'protection of privacy' arises from a false notion that what is on CCTV is somehow available for national television. It is not. The CCTV from slaughter houses is not. Nor is police cell or shoulder-camera footage.
Vulnerable people need protection from abuse, by staff or by their peers. CCTV footage, available only to authorised monitors, but possibly sometimes including a glimpse of them receiving personal care, is not a threat to them. Lack of CCTV is.