London's Planning Portals Hit by Duplicate Image Crisis — Here's What Changed This Week

London's network of borough planning portals has spent the past week firefighting a duplicate image problem that caused uploaded site photographs, architectural drawings and supporting documents to appear multiple times within individual planning applications — in some cases stacking the same image dozens of times and inflating file sizes to the point where case officer systems slowed to a crawl. The fault, which first surfaced late last month, became acute enough by Monday 29 June that several boroughs quietly suspended online submission windows while their IT teams worked alongside third-party platform providers to isolate the error.

The timing matters. The Starmer government's planning reform agenda, anchored in the Planning and Infrastructure Bill currently before Parliament, is pushing local authorities to digitise and accelerate decision-making. Mayor Sadiq Khan's London Plan policies already require faster processing of applications for housing on small sites. A technical failure that bogs down the very digital infrastructure councils are supposed to be modernising cuts against that political grain at exactly the wrong moment.

Which Boroughs Were Affected — and What They Did About It

Tower Hamlets and Southwark were among the councils most visibly affected. The Planning Portal used by Tower Hamlets — which covers high-density development corridors along Whitechapel Road and around the Blackwall Reach regeneration zone — was logging duplicate image entries on submitted applications from at least 23 June onwards, according to public-facing case file records visible on the council's planning search pages this week. Southwark, handling a bulging caseload of applications tied to the Elephant and Castle and Old Kent Road Opportunity Areas, issued a brief notice on its planning pages on 1 July advising applicants that document uploads should be checked manually before submission until further notice.

The underlying issue traces to a rendering and caching behaviour in the document management layer used by Planning Portal, the national platform operated by TerraQuest Solutions under contract to the Planning Advisory Service. When applicants uploaded PDF packs containing multiple embedded images — common in design and access statements — the system was in some instances duplicating each image asset as a standalone file, attaching all versions to the live case record. For case officers reviewing applications on screen, the effect was disorienting and time-consuming to unpick.

Smaller borough teams without dedicated digital planning officers felt the strain most acutely. A planning application for a three-storey residential conversion on Coldharbour Lane in Lambeth, submitted on 26 June, reportedly carried forty-seven image entries where the applicant had uploaded seven. The application remains validated but has not yet been registered for public consultation as of Friday.

The Fix, and What Applicants Should Do Now

TerraQuest pushed a patch to the back-end rendering pipeline on Wednesday 2 July. Boroughs using the national portal were advised to clear cached document records for affected applications and re-ingest source files. The company has not issued a public statement, and the Planning Advisory Service's website carried no advisory notice as of Friday morning. Several borough planning departments have updated their own FAQ pages to acknowledge the issue.

For anyone with an active application, the practical steps are straightforward. Log into your Planning Portal account, navigate to the submitted application, and check the document list under the supporting documents tab. If you see the same file name appearing more than once, contact your local authority's planning validation team directly — in London that typically means emailing the borough's planning inbox with your application reference number and a note flagging the duplication. Do not re-submit the application, as this generates a new reference and restarts the statutory clock.

The statutory determination period for most householder applications is eight weeks from validation. Any application caught in the duplicate-image backlog and not yet formally validated has not started that clock. Applicants in boroughs including Tower Hamlets, Southwark and Lambeth should factor in a potential delay of up to two weeks beyond their original expected validation date when planning contractor or builder start dates. With the government pushing councils to hit a target of 300,000 new homes nationally per year, even a fortnight's friction in London's busiest planning queues adds up fast.