It is not enough to just remove the patient identifiable information.
'You must remove the entire record for each patient who has opted out from the prepared data before it is disclosed (not just remove the identifiers). Data should not be removed from the patient’s original medical/care record.'
https://digital.nhs.uk/services/national-data-opt-out/compliance-with-the-national-data-opt-out/compliance-implementation-guide#before-you-start