How London's Planning System Became Buried in Duplicate Images — and Why That Problem Is Finally Being Fixed

London's planning departments are sitting on a backlog problem that has nothing to do with staff numbers or political will. Across the 32 boroughs and City of London Corporation, digital planning portals built at different times, by different contractors, using different standards, have accumulated hundreds of thousands of duplicate image files — site photographs, design drawings and heritage assessments filed more than once, sometimes under different application numbers, sometimes under the same one. The result is a records system that planning officers describe internally as unworkable at scale.

The issue matters now because the Labour government has staked a significant part of its domestic programme on accelerating housing delivery. The Planning and Infrastructure Bill, introduced at Westminster in 2025, explicitly requires local authorities to process more applications faster. But speed requires clean, searchable data. Duplicate images bloat storage, break automated search tools and — critically — cause case officers to spend time manually cross-referencing files that should be instantly retrievable.

How the Duplication Accumulated

The roots of the problem stretch back to the early 2000s, when councils began scanning paper planning archives. Tower Hamlets, Southwark and Lewisham each ran separate digitisation programmes, often contracting the work out to different firms with no shared file-naming convention. When the Planning Portal — the national online submission system — launched its upgraded platform in 2013, it ingested legacy data from those local systems without deduplication. Files migrated in bulk. If a document had been saved twice locally, it arrived at the central system twice.

A 2022 review by the Planning Advisory Service, an organisation funded by the Ministry of Housing, Communities and Local Government, identified data quality as one of the top five barriers to planning digitalisation across English councils. The review did not publish borough-by-borough figures, but it noted that image duplication was a systemic rather than isolated issue, concentrated in authorities that had undergone multiple IT platform changes. London, with its fragmented borough structure and long history of redevelopment activity — think the Olympic Park legacy work in Newham, or the decade-long regeneration of Elephant and Castle in Southwark — is disproportionately affected.

The Greater London Authority's London Datastore, maintained by City Hall, has flagged the inconsistency problem in annual data quality reports since at least 2019. Planning data submitted by boroughs to the GLA for strategic oversight regularly contains duplicate reference numbers and repeated image attachments. A GLA technical note published in March 2024 recorded that roughly 12 percent of planning application records submitted to the datastore in the preceding 12 months contained at least one duplicate document attachment, with image files accounting for the largest share.

What Is Being Done — and What Comes Next

The Office for Digital Planning, a unit within the Department for Levelling Up that survived into the current administration under a revised remit, has been piloting a deduplication tool since January 2026 with a cohort of six councils, including Hackney and Brent. The tool uses hash-matching — a process that assigns each file a unique digital fingerprint — to flag identical images regardless of what they have been named or where they have been stored. Early results from the Hackney pilot, presented to a Local Digital Fund working group in May 2026, suggested that around 18 percent of image files in the borough's active planning caseload were duplicates or near-duplicates.

Brent Council's planning team, based at its Wembley civic centre on Engineers Way, has also been working with the GLA's digital team to reclassify misfiled heritage photographs from the South Kilburn regeneration programme — one of the most document-heavy estate renewal projects in north-west London — ahead of a planned data migration later this year.

For residents and developers, the practical effect of a cleaner system should be shorter waits. Under the Planning and Infrastructure Bill's proposed timeline, major applications should be decided within 26 weeks. That target is unreachable if case officers are manually sorting image folders. The deduplication rollout is scheduled to reach all London boroughs by the end of the first quarter of 2027, though that timeline depends on MHCLG funding allocations confirmed in the autumn spending review. If the money arrives on schedule, the backlog that quietly accumulated over two decades could, at least in principle, be cleared within 18 months.