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

London's planning departments are sitting on a problem that has been building since the early 2000s: hundreds of thousands of duplicate images clogging digital case management systems across the capital's 33 boroughs. The issue, long treated as a low-priority administrative headache, is now drawing serious attention as the Labour government pushes its planning reform agenda and borough councils face pressure to approve more homes, faster.

The roots of the problem are mundane but consequential. When councils began digitising paper planning files in earnest — a process that accelerated after the Planning and Compulsory Purchase Act 2004 mandated more accessible public records — scanning contractors were paid per document. That created a financial incentive to scan the same site photograph, elevation drawing or officer report more than once. Some files were migrated between systems two or three times as councils upgraded their software, each migration duplicating attachments that had already been duplicated.

How the Backlog Built Up

The London Borough of Southwark, which manages one of the busiest planning caseloads in England owing to the scale of regeneration along the Old Kent Road and around Canada Water, began an internal audit of its document management system in late 2024. The audit, which was referenced in a committee report published in January 2025, found that a significant proportion of image files attached to historic planning applications were exact or near-exact copies stored under different reference numbers. The problem was not unique to Southwark — Tower Hamlets, which has processed thousands of applications related to the Isle of Dogs and Poplar Riverside development zones, flagged similar findings to the Planning Advisory Service that same year.

The Greater London Authority's London Plan team has been aware of the systemic issue since at least 2022, when a review of the GLA's own spatial data infrastructure identified redundant assets slowing search and retrieval times across the Mayor's planning portal. Sadiq Khan's office commissioned a broader digital infrastructure review in 2023, part of which examined how duplicate records were affecting the speed of strategic planning decisions on schemes of more than 150 units — decisions that legally must be completed within defined statutory periods.

The practical consequences are real. Planning officers searching case histories to assess precedent on a street like Tooley Street in Bermondsey, or reviewing cumulative impact assessments for Elephant and Castle's ongoing mixed-use development, can waste significant time navigating repeated files before reaching the actual decision notices they need. Where AI-assisted document review tools have been piloted — including a 2024 trial run by Hackney Council using software procured through the Crown Commercial Service — duplicate images degraded the accuracy of automated summaries, because the same visual information was weighted multiple times.

What Comes Next

The Planning and Infrastructure Bill, currently making its way through Parliament, includes provisions that would push councils toward standardised digital submission formats — a change that planning technology consultancies argue would reduce new duplicates entering the system from 2027 onward. But it does nothing to address the existing backlog. The Department for Housing, Communities and Local Government has allocated funding through the Planning Skills Delivery Fund, which in its 2025-26 round distributed £46 million across English local authorities, though the specific allocation earmarked for digital record remediation has not been separately itemised in published guidance.

Several boroughs are now piloting deduplication software independently. Lambeth Council began a phased rollout in April 2026, targeting applications submitted before 2010 first, given those records tend to carry the highest volume of repeated scans. The work is unglamorous and largely invisible to residents, but its effects will be felt. Faster document retrieval means faster officer reports. Faster officer reports mean planning committees can process more applications per cycle. In a city where the housing shortage is measured in the tens of thousands of units, shaving days off individual decisions adds up. The boroughs doing this work quietly, in server rooms rather than press releases, may end up mattering more to London's housing future than anyone currently credits them for.