A significant cyber security incident has affected Westminster City Council, the Royal Borough of Kensington and Chelsea (RBKC), and the London Borough of Hammersmith and Fulham. These councils share elements of their IT infrastructure, which means a single breach has caused a wide level of disruption. As a result, key public services, including planning and building control, are experiencing severe delays.
The attack occurred during the weekend of 24 to 26 November 2025 and led to an immediate shutdown of digital systems.
Following a detailed investigation carried out with cyber security specialists from NCC Group, the council has confirmed that unauthorised individuals gained access to its systems and copied data. Although the incident was contained at an early stage, the council has stated that there is no indication the breach extended to external or third party systems. Initial findings suggest that some of the material taken includes personal and potentially sensitive information.
The Information Commissioner’s Office was informed straight away, and the council is now working closely with the police and the National Cyber Security Centre to understand the full extent of the breach and to identify those responsible. Residents have been advised to follow official NCSC guidance on protecting their personal information and remaining alert to possible scam activity, as there is a risk the data could be misused or released.
RBKC has already written to more than 100,000 households with practical advice on reducing the risk of fraud and identity theft. Particular attention is being given to reviewing information linked to vulnerable individuals, although the council has confirmed that a complete assessment of the data involved is likely to take several months.
The incident has had a noticeable impact on council operations. Some services have experienced slower response times, phone disruptions, and delays affecting revenues, benefits, and housing processes. Certain payments and Direct Debit collections have also been disrupted, although the council has confirmed that essential services continue to operate.
For anyone with a live planning application in Westminster or RBKC, or those preparing to submit new applications, the impact is considerable. The disruption affects:
In practice, this means that planning applications may take far longer than usual to progress through the system. Some services are currently unavailable, and others are operating with significant limitations. Westminster Council has confirmed publicly that full restoration will take time and that delays should be expected across all planning functions. The council confirmed to 4D Planning that as of 4th December, no applications have been processed in over a week.
Planning timelines in London are already stretched, and any interruption can affect project programmes, contractor appointments and financial commitments. For applicants working to tight deadlines, a delay in validation or a slip in determination dates may create real frustration. Developers, architects and property owners should factor additional time into their schedules until council systems stabilise.
This situation also shows how reliant the planning system has become on digital infrastructures and how vulnerable the process can be when those systems fail. With three major London boroughs affected at the same time, the impact is felt across a very large number of ongoing applications.
During periods of uncertainty, it becomes more important than ever to ensure that your application is well prepared, complete and ready for immediate processing once the council systems recover.
4D Planning can assist by:
We continue to monitor Westminster and RBKC (Royal Borough of Kensington and Chelsea) Planning Departments for service updates and will provide further guidance as more information becomes available. Watch this space.
If you are preparing to submit an application, you may wish to proceed with all preparatory work while accepting a delay in validation. If your application is already in the system, maintain realistic expectations and allow extra time for responses. If your project is time sensitive, contact us at 4D Planning so we can help you manage risk and adjust your programme accordingly.
The councils are issuing updates through their websites, though availability may vary during the recovery period. The latest statement from Westminster and RBKC Council can be found on their news page.
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