A review of redacted documents released by Thurrock Council under freedom of information and subject access laws has uncovered a series of disclosure failures involving sensitive information. The material includes witness names, police operational information, bank details and other confidential data.
Documents disclosed by Thurrock Council, in response to a Freedom of Information Act (FOI/4094) and subject access requests, between September 2025 and June 2026 did not, in a number of cases, adequately remove third-party or sensitive information. Instead, material that appeared to have been deleted could still be recovered as so-called “hidden data”.
Thurrock Council was notified by one of the recipients of the subject access request as soon as the issue was identified.
The issue was uncovered during the East Anglia Bylines Spotlight Team’s continuing investigation into NATIS and related matters. A subsequent review of documents obtained through freedom of information and subject access requests identified a number of similar examples spanning a nine-month period.
The revelations
The freedom of information and subject access requests related to the Spotlight Team’s continuing investigation into the Counter Fraud Investigation Directorate (CFID), a joint operation involving Castle Point, Southend and Thurrock councils, and South Essex Homes, between 2016 and 2019. In 2018 the unit adopted the name National Investigation Service (NATIS), before being run solely as a Thurrock Council department from 2019 until 2025.
The improperly redacted information included, but was not limited to:
- the identities of whistleblowers;
- the names of witnesses;
- the name of a police or NATIS operation;
- the nature of information disclosed by Bedfordshire Police to NATIS;
- specific details of a criminal offence committed in Luton;
- the way in which information was to be recorded, including in hard copy;
- the personal details of third parties, witnesses and others arrested by CFID, including names and contact details;
- bank details, including account numbers and sort codes, belonging to several individuals;
- the names of officers and staff at Thurrock and Southend working on cases;
- information given confidentially by third parties to investigators; and
- details of two people whom CFID/NATIS planned to arrest.
Is ‘hidden data’ an issue?
The Information Commissioner (IC) defines “hidden data” as personal information that is not immediately apparent to someone viewing a document on a computer screen or mobile device. Information may be obscured for entirely legitimate reasons, including compliance with data protection law. Yet what is straightforward on paper, blacking out a word, for example, can be considerably more precarious in an electronic document.
Simply placing a shape over text, or changing the colour of words to match the background, may be sufficient if the document is printed. Digitally, however, such methods may leave the original information intact beneath the surface. Open the file in different software, or convert it to another format, and the concealed material may reappear.
In an age of multiple file formats, apps and devices, uncovering hidden information need not require technical sophistication; it can happen by accident.
The IC has issued guidance intended to prevent precisely this sort of event: the disclosure of sensitive material apparently hidden in a document but not actually removed from it.
Thurrock isn’t alone
Perhaps the best-known recent example of hidden data involved widely reported problems with redactions in the Epstein files, but the issue has also affected police forces and local authorities in the UK. Also, a single disclosure failure can affect multiple people.
In 2024, Southend Council avoided a substantial fine after it failed properly to redact or remove staff wage and personal information from a Freedom of Information Act response.
In July 2025 Suffolk County Council reported that it had seen the fourth consecutive increase, year on year, in the number of security incidents, which rose from 670 in 2024 to 724. Of those, 338 resulted in personal data breaches, of which 283 involved vulnerable children and adults.
Human error can also play a part. In June 2026, Norfolk Police reported itself to the Information Commissioner after inadvertently sending officers’ and staff payroll information to a former officer.
Why it matters
The concern is not confined to the information already uncovered. The larger question is how much other material may remain “hidden” but nevertheless still be accessible in disclosures made during the same nine-month period.
As a unitary authority, Thurrock Council handles some of the most sensitive personal information held by public bodies. The discovery raises obvious questions about whether similar disclosure issues may exist beyond the cases identified so far.
At the time of writing, the scale of the exposure remains unclear.
A spokesperson for Thurrock Council said: “Thurrock Council is aware an error was made in the redaction in response to the FOI disclosure sent to Stuart Burrell. Mr Burrell has worked with the Council to return the documents, destroy any copies and received his assurance that the documents have not been sent to anyone, and we have received assurances he will not share the redacted information with anyone else.
“We will establish how the error occurred in this response as it did not conform with our standard practice in redaction. Thurrock Council has also reported itself to the ICO, which has confirmed it will not be investigating based on the actions taken by the Council and has issued advice to prevent future errors of this nature.”
Southend City Council was also contacted for comment but has yet to respond.
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