i do not know the answer directly, but there was a whole system in place for storage of records of interviews held under PACE. Themachine makes two copies. The inteviewee is asked which he wants to be be sealed. It is so sealed and goes off for stirage. The other is used for all practical m atters.
The Master tape is then accessible only on the order of a crown court judge. From rather dim memory, I think that such orders were extremely rare.
That system made sense for that technology. I am not sure that it would make sense for such a system to be copied for body camera footage, but elements of it may be inherited.