London Leads on Scrubbing Duplicate Images From Planning Records — But Other Global Cities Are Catching Up Fast

Southwark Council confirmed this week that it has cleared more than 340,000 duplicate image files from its planning portal since January, the largest single clean-up operation carried out by any London borough since the government's Planning and Infrastructure Bill began pushing local authorities to digitise their records. The exercise, part of a broader shift toward machine-readable planning data mandated by the Department for Levelling Up, Housing and Communities, has put London at the front of a quiet but consequential race among global cities to get their archives in order.

The timing matters. Keir Starmer's government has staked a significant part of its housing agenda on faster, more transparent planning decisions. Ministers have argued repeatedly that bloated, duplicated and inconsistent digital records slow down decisions on new homes, delay appeals and inflate the cost of Freedom of Information requests. With the Planning and Infrastructure Bill moving through its Lords stages, councils have a direct financial incentive — and, shortly, a legal obligation — to standardise what they hold.

What London Is Actually Doing

Southwark is not alone. The Greater London Authority's London Datastore programme, which aggregates planning and land-use data from all 33 boroughs, flagged in its June 2026 quarterly report that duplicate image records — scanned site photographs, elevation drawings and heritage photos uploaded multiple times under different file names — accounted for roughly 18 percent of total storage across participating boroughs. That figure, drawn from the GLA's own audit, has prompted boroughs from Hackney to Hillingdon to run algorithmic deduplication tools against their back catalogues.

Tower Hamlets, which holds one of the largest concentrations of live planning applications in the country owing to continued development pressure around Whitechapel and Canary Wharf, began a phased deduplication programme in March 2026 using open-source perceptual hashing software. The borough's digital planning team told The Daily London the process had already reduced active storage load by around a fifth, freeing capacity for higher-resolution documents on new applications. Camden, meanwhile, partnered with the Open Digital Planning project — a consortium backed by the Ministry of Housing — to build a shared image registry that prevents duplicate uploads at the point of submission rather than cleaning them up afterwards.

London's approach contrasts sharply with what is happening in several peer cities. New York City's Department of City Planning still relies heavily on PDF bundles for submitted drawings, with no borough-level deduplication standard in place as of June 2026. Paris, which overhauled its permis de construire system in 2023, has a centralised national portal under the Ministère de la Transition Écologique that theoretically prevents duplicates, but arrondissement-level uploads continue outside that system. Amsterdam's Omgevingsloket, introduced under the Dutch Environment and Planning Act that came into force in January 2024, is the closest European comparator: it enforces a single-upload rule per document type, which planning data specialists have cited as a benchmark.

Why It Costs Real Money

Storage is cheap, but retrieval is not. The Local Government Association estimated in a 2025 report that English councils collectively spend around £47 million a year on planning-data management, a figure that includes staff time spent locating correct document versions during appeals and public inquiries. When an inspector at the Planning Inspectorate in Temple Quay House, Bristol, needs to cross-reference a heritage photograph from a 2009 application in Bermondsey against a current scheme on the Old Kent Road, duplicate files can add hours to a review.

For Londoners watching planning decisions drag on — and the capital's housing delivery remains well below the 88,000 new homes a year the GLA has identified as needed — the back-end data question is less abstract than it sounds. Faster, cleaner records mean faster decisions. The Open Digital Planning project is due to publish its next set of borough compliance figures in September 2026, which will provide the clearest snapshot yet of how much progress has actually been made. Boroughs that have not begun deduplication by that date are expected to face formal guidance letters from the Ministry of Housing. For councils still sitting on unaudited archives, the window is narrowing.