How London's Planning System Got Buried in Duplicate Images: The Paper Trail Behind a Digital Crisis

London's planning departments are carrying a hidden administrative burden: tens of thousands of duplicate images clogging their digital document systems, slowing down case officers and in some instances delaying planning decisions by weeks. The problem is not new, but the scale of it is only now becoming clear as boroughs push ahead with data-sharing requirements under the Levelling-Up and Regeneration Act 2023, which mandates that local planning authorities publish machine-readable data by 2025.

The issue matters now because Keir Starmer's government has staked a significant portion of its housing agenda on faster, more transparent digital planning. The Ministry of Housing, Communities and Local Government has been pressing councils to clean up their data pipelines ahead of the Planning and Infrastructure Bill's passage through Parliament. Duplicate images — scanned floor plans, site photographs, and heritage assessments uploaded multiple times under different file names — sit at the centre of that clean-up problem.

How the Duplication Built Up

The roots go back to 2009 and 2010, when the then-Labour government pushed councils to digitise legacy paper files. Most London boroughs contracted this work out to third-party scanning firms, and the handover was messy. Southwark Council, for instance, inherited a backlog of roughly 80,000 planning applications on paper when it transitioned to its electronic document management system. Files were often scanned more than once to ensure nothing was missed, and version-control discipline was inconsistent.

By the mid-2010s, budget pressures across the capital meant the teams responsible for data hygiene were stripped back. Tower Hamlets, one of the boroughs with the highest volume of major planning applications in London, saw its planning support staff numbers fall alongside wider local government cuts. Similar stories played out in Hackney, Ealing, and Newham. Without dedicated resource to audit what had been uploaded, duplicate images multiplied quietly inside systems like Idox Uniform and Northgate — the two document management platforms used by the majority of the capital's 33 boroughs.

The Greater London Authority's London Development Database, which aggregates planning data from all boroughs, began flagging image duplication as a systemic issue in its 2021 data quality review. That review found that in some borough datasets, up to 18 per cent of uploaded image files were duplicates of existing records. The GLA asked boroughs to self-report and remediate, but progress was patchy — only 11 of 33 boroughs had submitted updated, cleansed datasets by the end of 2022.

The Cost and What Comes Next

Fixing the problem is not trivial. Image deduplication at scale requires either expensive software licensing — specialist tools from suppliers such as Precisely or Aparavi carry annual fees that smaller boroughs cannot easily absorb — or manual review, which is slower and ties up planning officers who are already stretched by the post-pandemic application surge. Camden Council, which covers areas including King's Cross and Hampstead, has been piloting an automated deduplication workflow since January 2026, though results have not yet been published.

The stakes are practical as well as administrative. Under the new national planning data standards being rolled out from 2025, duplicate images can cause application reference numbers to fail validation checks, which in theory could stall a decision notice being issued. For a major mixed-use scheme on somewhere like the Old Kent Road in Southwark — where several large regeneration projects are currently in the pipeline — a bureaucratic delay of even a fortnight carries real financial consequences for developers and, ultimately, for housing delivery targets.

For Londoners watching the housing crisis worsen, the message from people working inside these systems is that the digital infrastructure underpinning planning is fragile in ways that do not make headlines. The MHCLG has said it expects all local planning authorities to meet the data publication standards by December 2026. Boroughs that have not yet audited their image libraries should treat that deadline as a hard one. Those that want to get ahead of it can apply for Planning Improvement Capacity funding, a grant programme administered through the Planning Advisory Service, which has been accepting applications since April 2026.