Which force it lands withOne national portal takes bad-driving footage from dashcams, helmet and house cameras, and sends it to the force policing that road. Across Greater London that is the Metropolitan Police, bar the Square Mile and its own City of London force. Past that: Hertfordshire, Essex, Kent, Surrey.
Fourteen days, and that is allCertain offences oblige a force to put a notice of intended prosecution in front of the registered keeper. Fourteen days is the whole of it, and once they have run, picture quality no longer matters. Forces close their own submissions earlier still, so look up what yours asks for before uploading.
What falls to youHave the other registration ready. What you saw goes on the record in a witness statement you have signed, and you may be asked to attend court and say it yourself. The footage says whatever it says; standing behind that is your half of the job.
Body-worn cameras on staffPoint a body-worn camera at anybody recognisable and UK GDPR has you processing personal data. Duties arrive with that: a lawful basis; signs put up where they can go; storage under your own control; and a reason behind however long you keep the material. In evidence it behaves as CCTV does — original kept, copies hashed, every hand-over logged.