London, January 13, 2026 – Explosive revelations from unredacted planning documents obtained by The Telegraph have intensified concerns over China's proposed "super embassy" in central London, exposing a vast underground network of 208 secret rooms, including one positioned alarmingly close to the UK's most sensitive fiber-optic cables carrying financial and communications data.
The new diplomatic compound, set to be built on the site of the former Royal Mint near the Tower of London, would span approximately 22,000 square meters and become China's largest embassy in Europe. Public versions of the plans had heavily redacted key sections, citing "security reasons," prompting former UK Housing Secretary Angela Rayner to delay approval and demand further clarification.
The unredacted blueprints, revealed on January 12 by The Telegraph, detail an extensive subterranean complex. A particularly concerning feature is a hidden triangular underground chamber—measuring up to 40 meters across and 2-3 meters deep—located beneath the Seamen’s Registry building on the site's north-west corner. This room sits just over one meter from high-speed fiber-optic cables running beneath Mansell Street.
These cables, owned by companies including BT Openreach, Colt Technologies, and Verizon Business, form a critical artery linking the City of London financial district with Canary Wharf. They handle massive volumes of financial transaction data, bank clearances, trading instructions, emails, and instant messaging for millions of users. The network connects to multiple data centers, serves as a core hub for the London Internet Exchange (LINX), and links to transatlantic cables extending to the United States—making it essential to the daily functioning of Britain's financial system.
The chamber includes at least two hot-air extraction systems, suggesting the potential installation of heat-generating equipment, such as high-performance computers possibly for data processing or interception. Plans also indicate China intends to demolish and rebuild the chamber's outer wall facing Mansell Street, placing construction personnel in extremely close proximity to the cables during work.
University of Surrey cybersecurity expert Professor Alan Woodward warned that such proximity creates "enormous temptation" for intelligence gathering. Known techniques for intercepting fiber signals—including rerouting, installing splitters, or bending cables to leak light—are feasible with physical access, and the wall reconstruction itself raises a "red flag."
Additional redacted elements include backup generators, high-voltage power facilities, communications pipelines, new elevator shafts, and underground bathrooms and showers—indicating the spaces could support prolonged underground activity. The underground areas are interconnected via passages leading to a large parking facility.
While no concrete evidence confirms detention facilities, the site's location near the Wapping Telephone Exchange and several data centers has heightened fears in security and political circles about risks to sensitive data.
The disclosure comes just weeks before Prime Minister Keir Starmer's expected visit to China to meet President Xi Jinping later this month. Critics accuse the Labour government of rushing approval, with Conservative shadow minister for national security Alicia Kearns labeling the project a potential "launchpad for economic warfare" at the "central nervous system" of UK critical infrastructure. She questioned how the government could overlook such evident risks.
A UK government spokesperson stated that national security remains the top priority, with security experts involved throughout the assessment process, and that all identified risks have been "addressed." The final decision rests with the Secretary of State for Housing, Communities and Local Government.
The controversy dates back to the Conservative era, when former Prime Minister Boris Johnson's chief adviser Dominic Cummings revealed MI5 and MI6 warnings that China aimed to construct a "spy center" underground.
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