How London's Planning System Got Buried in Duplicate Images — and What's Being Done About It

London's 33 planning authorities are sitting on a backlog problem that predates the current housing crisis but has been made significantly worse by it. Duplicate images — photographs, site plans, and architectural drawings filed more than once against the same application — now account for a measurable share of the document load held across borough portals and the Greater London Authority's own planning database. The issue is not new. But how it became entrenched, and why it matters right now, requires understanding nearly two decades of piecemeal digitisation.

The roots go back to 2008, when the government mandated electronic submission of planning applications under the then-Planning Portal system. Boroughs scrambled to comply, and many adopted their own document management platforms alongside the national portal. The result was fragmentation: a single application could end up mirrored across multiple systems, with supporting images uploaded separately to each. Camden Council, for instance, ran its own Idox-powered back-end alongside the national portal well into the 2010s, and similar arrangements existed in Southwark and Tower Hamlets. Every resubmission, every revision, every agent who re-uploaded a site photograph rather than linking to an existing file added another copy to the pile.

Why the Problem Compounded Over Time

The volume of applications accelerated the damage. Between 2012 and 2019, the number of planning applications received annually by London boroughs grew steadily as permitted development rights were tightened and more works required formal consent. The Planning Portal itself underwent a major rebuild in 2020, migrating to a new platform that did not automatically deduplicate legacy documents carried over from the old system. Officers at authorities including Hackney and Lewisham have noted in publicly available committee reports that document retrieval times on complex applications slowed as database sizes swelled.

The current Labour government's planning reforms add fresh urgency. The Planning and Infrastructure Bill, introduced earlier this year, places new obligations on local planning authorities to process applications faster and to make their decision records more accessible for public scrutiny. The target — enshrined in the bill's impact assessment — is to reduce the share of major applications decided outside the statutory 13-week period. Duplicate and misfiled images slow down that process directly: officers searching for the correct version of a revised floor plan must manually identify which of several identical-looking files is current.

At the Greater London Authority, the London Development Database has been the subject of periodic data-quality audits since 2019. The GLA's Planning Datahub, launched in 2023 as part of a broader open-data initiative, was specifically designed to impose consistent file-naming and metadata standards on submissions flowing through it. But the Datahub covers new entries; it does not retrospectively clean the archive of applications decided before its launch, which runs to hundreds of thousands of records stretching back to the mid-2000s.

The Cost of Inaction

Storage costs are not trivial. Cloud hosting for local authority document management systems is typically charged on a per-gigabyte basis, and several boroughs have moved to Microsoft Azure or Amazon Web Services contracts in recent years. Redbridge and Brent both completed data centre migrations between 2022 and 2024. Duplicate images that sit unreferenced in those archives do not cost much individually, but across a system holding millions of documents the overhead accumulates. More practically, the duplication complicates the government's ambition to create a genuinely open, machine-readable planning record that proptech developers and housing researchers can query reliably.

The immediate path forward involves two tracks running in parallel. The Planning Portal operator, a not-for-profit company owned jointly by the Local Government Association and central government, has been trialling automated deduplication tools on a pilot group of boroughs since early 2026. Separately, the GLA is working with Ordnance Survey under the National Land Data Programme to establish unique identifiers for every planning document, which would make accidental duplication detectable at the point of upload rather than years after the fact.

For Londoners tracking a specific application — say, a conversion in Bermondsey or a new block near Elephant and Castle — the practical advice is to use the Planning Portal's public access search rather than borough portals where possible, as the national system now flags superseded documents with a status marker. Checking that marker before relying on any image or drawing is currently the most reliable safeguard while the deeper infrastructure work continues.