How London's Planning System Ended Up Buried Under Duplicate Images — and What's Being Done About It

London's overstretched planning departments are grappling with a problem that sounds mundane but has real consequences: tens of thousands of planning applications held in public portals across the capital contain duplicate image files, often the same floor plan, elevation drawing or site photograph uploaded multiple times under different file names. The result is bloated case files, slower processing times, and a public record that is harder for residents, architects and developers to navigate.

The issue matters now because Keir Starmer's government has made housing delivery the centrepiece of its domestic agenda, and local authorities are under direct pressure from the Ministry of Housing, Communities and Local Government to cut decision times on major applications. Duplicate documents are not a cosmetic irritant — they inflate the apparent volume of a submission, complicate automated document-parsing tools that councils are investing in, and can cause version-control errors where an officer reviews an outdated drawing rather than the current one.

How the Problem Accumulated Over a Decade

The roots go back to the mid-2010s, when most London boroughs migrated from paper-based systems to online portals, predominantly through two platforms: Idox's Uniform system and Northgate's Public Access. Neither platform, at the point of rollout, included robust duplicate-detection logic. Applicants and their agents — particularly busy practices filing dozens of applications a month — discovered it was simply easier to re-upload an entire document pack than to track which files had already been submitted. Councils, already short-staffed, rarely pushed back.

Tower Hamlets and Southwark, two of the highest-volume planning boroughs in London, both migrated to digital portals between 2014 and 2016. By the early 2020s, case officers at both councils were internally flagging file management as a problem, according to planning consultants who work regularly with those authorities — though neither council has published a formal audit of the scale of duplication in its system. The Greater London Authority's Planning London Datahub, launched in 2019 to aggregate data from all 33 planning authorities, inherited whatever inconsistencies existed at borough level, meaning duplicates propagated upward into the city-wide dataset as well.

A 2023 review by the Royal Town Planning Institute found that digital casework inefficiencies — a category that includes duplicate documents alongside poor file naming and missing metadata — were contributing to delays across English local authorities. The RTPI estimated that case officers were spending a meaningful share of their working week on document management tasks that better-designed systems could automate, though the institute stopped short of putting a precise figure on the cost in London alone.

What Councils and the Mayor's Office Are Now Doing

Sadiq Khan's planning team at City Hall has been working with Hackney and Lewisham since early 2025 on a pilot to retrofit duplicate-detection algorithms into their public-facing portals, using file-hash comparison to flag identical image files before an application is formally validated. Hackney's planning portal, accessible via the council's website on Mare Street, E8, became the first in London to run the tool in live validation from March 2026. Lewisham followed in May 2026.

The GLA has said it wants all 33 boroughs using some form of automated duplication-checking by the end of 2027, aligning with the government's broader Planning and Infrastructure Bill, which passed its Commons stages this spring and contains provisions requiring local authorities to meet new digital standards for application data.

For anyone submitting a planning application in London right now, the practical advice is straightforward: check file names before uploading, use a consistent naming convention that includes drawing revision numbers, and confirm with the relevant borough's validation checklist — available on every council's planning portal — exactly which documents are required. Resubmitting a full pack to correct a single drawing is the single biggest driver of duplication and adds days to validation. Boroughs including Camden and Islington publish pre-application guidance specifically warning agents against bulk re-uploads. The time it takes a council to validate an application — currently averaging 15 to 20 working days across most inner London boroughs — starts only once the file is clean.