London Tackles Surge of Duplicate Images in Public Digital Spaces

London's public sector digital teams are quietly wrestling with a problem that has ballooned since 2024: duplicate and near-duplicate images flooding everything from the Greater London Authority's planning portals to Transport for London's passenger information displays. The issue, once considered a minor technical nuisance, has become a genuine governance headache as AI-generated imagery and recycled stock photography clog municipal databases, slow planning application reviews and erode public trust in official communications.

The timing matters. Sadiq Khan's office has pushed an ambitious digital infrastructure programme across City Hall and the 33 London boroughs, with planning reform central to the Labour government's agenda under Keir Starmer. When duplicate imagery contaminates planning submissions — the same rendered photograph of a proposed development submitted under slightly different filenames — case officers lose hours manually cross-referencing records. At Southwark Council's planning department on Tooley Street, officers have flagged internal concerns about the volume of near-identical images arriving alongside major Thames riverside development applications.

What London Is Doing — And What It Isn't

The GLA's Digital Team, based at City Hall near Tower Bridge, began piloting a perceptual hashing tool in early 2025 to flag duplicate images in planning submission portals. Perceptual hashing works by converting images into short numerical fingerprints; when two images produce fingerprints within a defined similarity threshold, the system raises an alert for human review. The pilot covered Lambeth, Lewisham and Tower Hamlets — three boroughs with the highest planning submission volumes south and east of the river. As of spring 2026, the GLA had not yet confirmed full borough-wide rollout, and smaller boroughs such as Richmond upon Thames and Kingston upon Thames remained outside any automated detection framework.

Compare that to Amsterdam. The Gemeente Amsterdam's digitisation office integrated automated duplicate detection into its omgevingsloket — its environment and planning portal — as early as January 2024, covering all 22 city districts simultaneously. The Dutch capital leaned on open-source tooling built by the Waag institute and mandated that any image file accompanying a planning submission be run through deduplication checks before a case reference number is assigned. No case number, no formal submission. London has no equivalent hard gate.

New York City's Department of City Planning took a different route. Following a 2024 audit by the city comptroller's office that found duplicate imagery in roughly 12 percent of environmental review submissions reviewed that year, the department introduced a vendor-managed image registry through its ZoLa mapping platform. Vendors must certify image provenance at the point of upload. The system is not perfect — certification can be gamed — but it created a paper trail that London's current process lacks.

Tokyo's Strict Approach and What London Could Learn

Tokyo's approach is the most rigorous of any major city studied by the Urban Digital Governance Forum, a Brussels-based research organisation that published comparative findings in March 2026. The Tokyo Metropolitan Government requires that all images submitted to its urban planning bureau carry embedded EXIF metadata confirming original capture date and location. Images stripped of metadata are rejected outright. The bureau processed 340,000 planning-related image files in the 2024 fiscal year and rejected approximately 4,200 on metadata grounds alone, according to the Forum's March report.

London processed an estimated 180,000 planning-related image submissions across its 33 boroughs in 2025, based on figures from the Planning Portal, the national submission platform used by English local authorities. No centralised figure exists for how many contained duplicates. That data gap is itself the problem.

For residents and developers, the practical upshot is straightforward: if you are submitting images to any London borough planning portal right now, label files clearly, retain original high-resolution files with intact metadata and avoid reusing photographs across separate applications. Submissions to Newham and Hackney in particular have faced delays linked to document management bottlenecks. The GLA has signalled it intends to publish updated digital submission guidance later this year, though no date has been confirmed. Until then, London remains a city with ambition on this front but without the hard infrastructure to match what Amsterdam built two years ago.