London Council Planning Portals Drowning in Thousands of Duplicate Images

More than 34,000 planning documents submitted to London borough councils in the twelve months to March 2026 contained duplicate or replacement image files that were never properly removed from the public record, according to figures compiled from Freedom of Information requests filed earlier this year. The backlog is quietly inflating application file sizes, slowing caseworker reviews, and — in several documented cases — causing approved plans to reference superseded drawings rather than the final agreed versions.

The timing matters. Keir Starmer's government has placed planning reform at the centre of its domestic agenda, with the Planning and Infrastructure Bill currently making its way through Westminster. Sadiq Khan's City Hall has separately pushed boroughs to digitalise their development management systems by the end of 2026. Both ambitions depend on clean, reliable data — and right now, that data is demonstrably messy.

Where the Numbers Are Worst

Tower Hamlets and Southwark show the sharpest concentrations of the problem among inner London boroughs, based on the FOI returns. Tower Hamlets processed roughly 4,200 planning submissions in the 2025–26 financial year. Of those, document audits flagged duplicate image attachments in approximately one in eight cases — a rate that caseworkers say stretches the borough's already pressured planning teams. Southwark, whose planning portal handles applications ranging from single-storey extensions in Peckham to major commercial schemes along the Old Kent Road regeneration corridor, recorded over 600 instances where an image marked as a replacement had not displaced the original file but had instead been appended alongside it.

The Greater London Authority's digital planning unit — based at City Hall on the Queen's Walk — has been piloting an automated file-validation tool since January 2026 as part of the London Development Database refresh. The pilot covers six boroughs and is designed to flag exact-match and near-duplicate images at the point of upload, before a file enters the formal register. Early internal metrics from the pilot, shared with the GLA's Planning Committee in April, suggested the tool reduced duplicate image incidents by around 40 percent in the pilot boroughs during its first quarter of operation.

Nationally, the Planning Inspectorate reported in its 2024–25 annual review that file-size inflation caused by redundant attachments was contributing to appeal case preparation times running an average of 11 days longer than the statutory target. London, which accounts for roughly a fifth of all major planning appeals, bears a disproportionate share of that delay.

What the Data Means for Applicants and Developers

For ordinary applicants — homeowners in Hackney trying to extend a kitchen, or small developers bringing forward a scheme near Bermondsey Street — the practical consequence is straightforward: the wrong drawing stays live on the public portal, objectors comment on a plan that no longer exists, and the caseworker must reconcile versions manually. That reconciliation, industry bodies estimate, adds between two and four weeks to determination timelines on affected applications.

The cost is not trivial. Planning consultancies working in central London typically bill at rates of £150 to £250 per hour for casework support. An additional three weeks of engagement on a mid-sized residential scheme — say, a ten-unit block in Islington — can add £4,000 to £8,000 to professional fees before a single brick is laid.

The GLA's digital planning pilot is due to conclude its evaluation phase in September 2026, with a recommendation expected before the end of the year on whether all 33 London boroughs should adopt the validation tool as a standard requirement. Applicants submitting documents in the meantime can reduce their exposure by maintaining a single numbered drawing register, clearly marking each file with a version date, and formally requesting that superseded images be removed from the public record in writing — a step that borough portals are legally obliged to action under the Local Government (Access to Information) Act 1985. It is a manual workaround for a problem that is, at its root, a structural one.