Your right to a copyOnce the video shows you as identifiable, under UK GDPR rules the operator must provide you with a copy. The operator has one calendar month after receiving your request to respond (although if your request is particularly complicated, or one of several made by you, this period may extend by up to another two months, but they must inform you of this within the first month). Anyone else who appears will be blurred before release, and unless there are unusual circumstances, no charge will be levied.
Put the hold in writingAn email on the day is worth more than a solicitor's letter a fortnight later. Send it immediately, stating which camera and which thirty minutes, and request in writing that the operator hold onto the footage.
When the police askWhen an officer asks and the operator says yes, that informal route is how most footage reaches a Thames Valley Police enquiry. If, however, the operator refuses, it becomes formal: first a data protection request and then an application to court.
Where we fit inAn accidental formatting of a disk. A recording device stopping on the night in question. An export removed from an office computer. All these generally come back for £400 + VAT, and in most cases you only pay if we recover your data. However, footage the loop has covered does not come back for anyone.