For more than ten years, Chinese state actors successfully infiltrated the United Kingdom’s classified computer systems, accessing low and medium-level government data in what security officials have described as a sustained and systemic breach. According to two former senior security officials and other government insiders, the intrusions granted Beijing access to information marked “official-sensitive” and “secret,” including confidential documents on policy development, private communications, and diplomatic correspondence. The compromised data, while not reaching the government’s top-secret tier, represents one of the longest and most extensive known foreign penetrations into British state infrastructure.
Officials familiar with the matter described China’s efforts to infiltrate British government systems as “endless,” with breaches occurring across multiple networks over the last decade. One major compromise involved a London-based data center used to store sensitive government information, which had been sold to an entity linked to China during a previous Conservative administration. The sale prompted significant security concerns, and ministers at the time briefly proposed destroying the facility before opting for alternative measures to secure it.
A spokesperson for the UK government confirmed that the country’s “most sensitive” information and the systems housing it remained uncompromised, despite the scale of Chinese intrusion attempts. The Chinese Embassy in London did not respond to requests for comment. The revelations arrive at a politically charged moment for Prime Minister Keir Starmer, who faces mounting criticism over his approach to Beijing following the failed prosecution of two men accused of spying for China. The Crown Prosecution Service cited the government’s historical reluctance to formally classify China as a national security threat as a factor in the case’s collapse.
Security experts have warned that the latest findings demonstrate the seriousness of Beijing’s cyber threat to the UK. While top-secret data remains secure, the exposure of “secret” materials — information that could seriously damage international relations or military operations if compromised — raises deep concerns about the resilience of British cybersecurity infrastructure. The government’s own classification framework identifies such data as requiring significant protection, though not the highest level reserved for information whose loss could threaten national security or cause widespread loss of life.
The controversy deepens as Starmer’s government faces internal and external pressure over its stance toward China. Critics have accused the prime minister of seeking to normalize relations with Beijing despite mounting evidence of espionage and cyberattacks. Within his cabinet, several members are urging him to block China’s application to construct a new mega-embassy in London. Meanwhile, senior diplomat Olly Robbins is in Beijing to negotiate terms for refurbishing the British Embassy there, a move that underscores the delicate balance of diplomacy amid rising security tensions.
The UK’s domestic intelligence agency, MI5, recently issued a warning to lawmakers about increasing espionage activities from both China and Russia. The National Cyber Security Centre reported a 50% surge in major cyberattacks over the past year, naming China as the “pacing threat.” These warnings echo previous reports that Chinese state-linked hackers have made sustained attempts to access Britain’s critical infrastructure networks, targeting everything from energy systems to telecommunications.
Former government officials have publicly corroborated aspects of the breach. Dominic Cummings, who served as Boris Johnson’s chief of staff, told The Times that “vast amounts of data classified as extremely secret and extremely dangerous for any foreign entity to control was compromised.” His account was partially supported by Tom Tugendhat, a former security minister, who confirmed that “the gist” of Cummings’s claims was accurate but declined to provide further details.
The long-term implications of the breaches remain uncertain, but they have already reignited debate over the UK’s cybersecurity posture and its relationship with Beijing. As evidence mounts of China’s persistent efforts to penetrate British systems, the government faces growing demands to reevaluate its diplomatic and security strategy toward one of the world’s most formidable cyber adversaries.
