Without prejudice to the processing of personal data for a purpose other than the purpose for which the data has been collected which is lawful under the Data Protection Regulation, the processing of personal data and special categories of personal data for a purpose other than the purpose for which the data has been collected shall be lawful to the extent that such processing is necessary and proportionate for the purposes -
(a) of preventing a threat to national security, defence or public security,
(b) of preventing, detecting, investigating or prosecuting criminal offences, or
(c) set out in paragraph (a) or (b) of section 47.