Recently we have had several requests for support regarding subject access requests that involve CCTV.
The ICO has some helpful general guidance in several places including https://ico.org.uk/for-organisations/uk-gdpr-guidance-and-resources/cctv-and-video-surveillance/ and this also offers a CCTV self-assessment checklist.
With particular reference to SAR’s and CCTV, you may also find https://ico.org.uk/for-organisations/advice-for-small-organisations/subject-access-requests-sar/subject-access-request-advice/#cctv helpful.