In 2019, the UK Department for Work and Pensions published their two-part staff guide on conducting fraud investigations. Privacy International went through the 995 pages to understand how those investigations happen and how the DWP is surveilling benefits claimants suspected of fraud.
https://privacyinternational.org/long-read/4395/shedding-light-dwp-part-1-we-read-uk-welfare-agencys-995-page-guide-conducting