How London's Planning System Got Tangled in Its Own Image Archive: The Story Behind the Duplicate Image Crisis

London's 33 borough planning portals contain tens of thousands of duplicate document images — scanned floor plans, site photographs and heritage assessments filed multiple times across overlapping systems — and the effort to clean up that backlog has quietly become one of the more expensive administrative headaches sitting on desks at City Hall and in borough town halls across the capital.

The problem did not emerge overnight. It is the accumulated consequence of two decades of piecemeal digitisation, during which individual boroughs built their own document management systems with little coordination between them. When the government's Planning Portal, run by TerraQuest Solutions, became the national submission gateway in the mid-2000s, local authorities were expected to integrate their legacy archives with the new platform. Many never fully did.

A System Built on Workarounds

The result is a layered mess. Southwark Council, to take one example frequently cited in planning circles, runs its public-facing portal alongside a back-end legacy system that predates the 2008 Planning Act reforms. Applications submitted through the national portal are automatically logged, but older scanned images — some dating to the late 1990s — sit in a parallel file store. When caseworkers retrieve documents, duplicate images surface routinely, sometimes showing the same elevation drawing four or five times under different reference tags.

Tower Hamlets faces a comparable situation. The borough processed more than 4,200 planning applications in the 2024-25 financial year, according to figures published by the Greater London Authority, and its digital records include a substantial volume of pre-2015 material that was bulk-scanned from paper files without deduplication protocols in place. Staff have described the process of locating a clean, single version of an older document as time-consuming, though the borough has not published a formal audit of the scale of duplication.

The national context sharpens the urgency. The Starmer government's Planning and Infrastructure Bill, currently making its way through Parliament, places significant weight on digitised, machine-readable planning data as a backbone for the new system of street votes and local design codes. The Department for Housing, Communities and Local Government has set a target for all local planning authorities in England to publish their data in an open, standardised format by the end of 2027. Duplicate and inconsistent image records directly undermine that ambition.

What Fixing It Actually Costs

Deduplication is not cheap. A procurement exercise run by the London Borough of Lambeth in early 2025 for a document management audit and cleansing contract drew responses ranging from £180,000 to over £400,000 depending on the scope, according to procurement documents published on the council's website at the time. Lambeth did not confirm which, if any, contract was awarded. Multiply that range across a significant share of London's 33 boroughs and the aggregate cost runs well into the millions — at a moment when most local authorities are managing constrained capital budgets.

The Greater London Authority's Digital Planning programme, launched under the mayoral office in 2023, has allocated funding to help boroughs standardise their data outputs, but that programme focuses primarily on live applications going forward rather than retrospective archive cleaning. Historic duplicate images remain largely the financial responsibility of individual boroughs.

For developers and architects working up applications at sites like the Old Oak Common regeneration zone in Ealing and Hammersmith & Fulham, or along the proposed Thameside West development corridor in Richmond, the practical friction shows up as delays when consultants attempt to cross-reference precedent decisions and find conflicting or repeated image sets in the public record.

The immediate practical step for anyone dealing with planning submissions in London is to use the national Planning Portal's own document checker before filing, flag duplicates explicitly in covering correspondence, and request confirmation from the receiving borough that only a single image set has been logged. It is unglamorous advice. But until the boroughs complete the archive work — and secure the funding to do it — it is the most reliable hedge against a system that is, for now, still catching up with itself.