How London's Planning System Ended Up Drowning in Duplicate Images — and What It's Doing About It

London's borough planning portals are carrying tens of thousands of duplicate image files — identical or near-identical documents submitted multiple times across separate planning applications — and the cumulative drag on case officers' time has quietly become a serious operational problem for at least a dozen local authorities across the capital.

The issue matters now because the Starmer government has staked a significant share of its domestic credibility on accelerating housebuilding, with a national target of 1.5 million new homes by the end of this parliament. Greater London specifically faces a target of roughly 88,000 new homes per year under the Mayor's updated London Plan benchmarks. Any bottleneck inside the planning machinery — even one that sounds as mundane as file management — has a measurable knock-on effect on decision timescales, and those timescales are already under intense scrutiny from developers, housing associations, and community groups alike.

How the Duplication Built Up

The roots of the problem run back to the mid-2010s transition to fully digital submissions. When the Planning Portal — the national online gateway operated by TerraQuest Solutions on behalf of local planning authorities — migrated boroughs onto its unified platform between 2013 and 2018, it inherited a fragmented ecosystem of legacy databases. Applicants submitting revisions to live applications discovered that the system offered no automatic deduplication check. A revised floor plan, for instance, could sit alongside the original under a near-identical filename, and officers had no reliable automated tool to flag the redundancy.

Tower Hamlets, one of the busiest planning authorities in England by application volume, started flagging the issue internally as early as 2019 according to published audit reports from the borough. Southwark Council's planning committee received a report in 2022 noting that case file bloat was contributing to slower officer review times on larger mixed-use schemes. The Greater London Authority's Planning and Regeneration directorate has acknowledged the problem in its own process reviews, though no single central body has owned the solution.

The scale is not trivial. A 2024 review commissioned by the Local Government Association found that English planning departments collectively spent an estimated 14 percent of case officer hours on document management tasks that could, in principle, be automated. Across a major authority receiving upwards of 8,000 applications per year — as Hackney and Lewisham both do — that translates into substantial lost capacity every working week.

What the Fix Looks Like

The government's Planning and Infrastructure Bill, currently making its way through the Lords, includes a clause requiring the Planning Portal to implement mandatory document deduplication and version-control checks for all major applications by January 2028. For London specifically, the Mayor's office is piloting a supplementary digital triage system at the Old Oak and Park Royal Development Corporation — the body overseeing what is described as Europe's largest regeneration project — where application volumes are expected to surge as HS2 construction milestones approach.

Several boroughs are not waiting for legislation. Islington Council began integrating an AI-assisted file-screening tool into its back-office system in March 2026, using software procured through the Government Digital Service's local authority framework. Camden is understood to be at the procurement stage for a comparable solution. Neither council has published outcome data yet, which makes independent assessment of early results impossible.

For applicants — architects, developers, self-builders filing through agents on streets from Bermondsey to Willesden — the practical advice from planning consultants is straightforward: adopt strict internal file-naming protocols before submission, check the current Planning Portal guidance on document categories, and confirm with case officers which revision supersedes which. It is basic hygiene, but it remains inconsistently practised.

The broader lesson from how London arrived here is familiar. A digital infrastructure decision made under budget pressure in 2013 deferred a problem that a small upfront investment in deduplication logic could have prevented. The bill for that deferral is now being paid in officer hours, delayed decisions, and homes that take longer to reach the people who need them.