London's Duplicate Image Problem: The Numbers Reveal a Growing Crisis in Digital Planning Records

London's planning system is drowning in bad data. Across 33 borough councils, digital planning portals contain an estimated tens of thousands of duplicate images — repeated photographs, mislabelled site plans, and redundant heritage photographs filed multiple times under different application references. The problem is not new, but the scale has grown sharply since the Planning Portal, the national digital gateway used by councils including Tower Hamlets and Southwark, migrated to its current infrastructure in 2020.

The timing matters. The Labour government has staked its domestic agenda on accelerating housing delivery, promising 1.5 million new homes nationally by 2029. Keir Starmer's administration has repeatedly pointed to planning reform as the mechanism to unlock that target. But planning officers in London boroughs say that swollen, poorly curated digital archives slow application processing — when a caseworker opens a file and finds 14 near-identical roof photographs submitted across three duplicate uploads, that officer loses time. Time, in a system already under acute pressure, is not a spare resource.

What the Numbers Actually Show

The Greater London Authority's digital infrastructure team does not publish a precise duplicate-image count, and individual borough figures are not aggregated centrally. However, Freedom of Information responses obtained by comparable local news organisations from boroughs including Hackney, Lambeth, and Greenwich have suggested that between 8 and 15 per cent of image files attached to planning applications filed since 2018 are duplicates — either identical files submitted twice within the same application, or the same photograph re-submitted across related discharge-of-condition applications.

At a borough the size of Lambeth, which received roughly 4,200 planning applications in the 2024-25 financial year, a 10 per cent duplication rate across associated image documents would mean tens of thousands of redundant files sitting in the council's document management system. Storage costs for local authorities are not trivial: cloud document management contracts for mid-sized London boroughs typically run between £80,000 and £200,000 annually, according to procurement frameworks published by the Crown Commercial Service.

The Planning Portal itself acknowledged in its 2023 annual review that file validation — the automated checking of submitted documents before they reach a case officer — remained an area requiring development. That review noted over 5.4 million documents were submitted through the portal that year nationally. Even a 5 per cent duplicate rate at national scale implies hundreds of thousands of redundant files entering council systems every 12 months.

What London Boroughs Are Doing About It

Some councils are beginning to act. Southwark Council, whose planning department covers areas from Bermondsey to Dulwich, has been piloting an AI-assisted document triage tool since early 2026, designed partly to flag duplicate uploads before they are assigned to case officers. The pilot, run in conjunction with a procurement process under the G-Cloud 14 framework, is expected to complete its assessment phase in the autumn.

The London Legacy Development Corporation, which manages planning applications across the Olympic Park and surrounding areas in Stratford and Hackney Wick, has used a bespoke document management system since 2022 that includes duplicate-detection logic at the point of upload — a setup not yet widely replicated across the mainstream borough planning portals.

For applicants — architects, developers, and private householders — the practical implication is straightforward. Duplicate submissions most commonly arise when applicants re-upload corrected drawings without withdrawing original files, or when agents submit the same supporting photograph under multiple document type categories. The Planning Portal's own guidance, updated in March 2025, recommends that applicants use unique file names incorporating drawing revision numbers and dates, and confirms that portal administrators can remove duplicate files on request, though this requires a formal correspondence process that few applicants know exists.

With the government's Planning and Infrastructure Bill still moving through Parliament, and pressure on councils to slash application turnaround times, boroughs that have not audited their image archives for duplication may find the issue surfacing in performance reviews before the end of 2026. The data is already there. Someone just needs to look at it.