How London's Planning System Got Tangled in Duplicate Image Records — and Why It Matters Now

London's planning infrastructure has a paperwork problem buried deep in its servers. Across the capital's 33 local planning authorities, duplicate image records — scanned documents filed twice, sometimes three times, under different reference numbers — have accumulated quietly for more than a decade, creating a backlog that planning officers say is now actively slowing the processing of applications. The issue has come into sharp focus as the Labour government pushes its Planning and Infrastructure Bill through Westminster, which would require councils to dramatically accelerate housing decisions.

The timing could not be more awkward. Keir Starmer's government has made housing delivery the centrepiece of its domestic agenda, setting a national target of 1.5 million new homes by 2029. In London, where Sadiq Khan's City Hall has its own target of 52,000 new homes per year, the efficiency of borough planning portals is not a back-office technicality — it is the front line of delivery.

How the Duplication Problem Built Up

The roots go back to the early 2000s, when individual boroughs began scanning paper planning files without any common technical standard. The Greater London Authority's Planning Data Unit has identified the problem as stemming from at least three separate waves of digitisation: an initial push around 2003, a second round triggered by the 2008 Local Democracy, Economic Development and Construction Act, and a third wave during the Covid-19 pandemic when councils rushed to move processes online between 2020 and 2022.

Each wave used different software. Tower Hamlets ran one document management system; Southwark ran another. Camden adopted a third platform in 2019 as part of its Digital Services Programme. When the Planning Portal — the national submission gateway operated by TeraPlan Ltd under contract since 2012 — began aggregating borough data for the government's Open Digital Planning project, the incompatibilities surfaced at scale. The same scanned elevation drawing for a single terraced house in, say, Lewisham High Street might appear under four separate image identifiers across two systems.

The Open Digital Planning project, a joint initiative between the Department for Levelling Up's successor body and the Greater London Authority, formally logged the duplication issue in a technical report published in March 2025. That report, which covered a pilot covering 12 London boroughs, found that roughly 18 percent of image assets in those databases were exact or near-exact duplicates. In practical terms, that means planning officers manually reviewing applications in boroughs including Hackney, Lambeth and Ealing were routinely opening and closing the same document multiple times without knowing it.

Why It Matters for Housing Decisions Today

The consequences are not merely administrative. Under current statutory rules, a local planning authority must determine a standard householder application within eight weeks. Major applications — large residential blocks, mixed-use schemes — carry a 13-week target. The Planning Inspectorate reported in January 2026 that London boroughs were missing those targets on 34 percent of major applications, one of the worst performance rates since comparable records began in 2010.

Campaigners at the London YIMBY network and planners at the built environment consultancy Iceni Projects have both argued publicly that back-end data quality is a structural cause of delay, not merely a symptom of under-staffing. The Greater London Authority is now funding a deduplication programme across six pilot boroughs — Newham, Greenwich, Haringey, Barnet, Croydon and Wandsworth — with £2.3 million drawn from the UK Shared Prosperity Fund. The programme is due to complete its first phase by December 2026.

For applicants and developers, the practical advice is straightforward: ensure every document submitted via the Planning Portal carries a unique file name referencing the application number, site address and document type. Several borough planning teams, including those at Lambeth and Islington, now include explicit file-naming conventions in their pre-application guidance notes, updated as recently as April 2026. Checking those guidance pages before submission takes minutes. Appealing a time-expired application because officers lost track of your drawings takes months.