Britain’s intelligence community is facing a storm of scrutiny and political finger-pointing after the collapse of a high-profile espionage case involving alleged Chinese spies. The fallout has reignited debate over the scale of Beijing’s covert operations in the UK, the effectiveness of British counterintelligence, and the government’s approach to an increasingly complex and risky relationship with China.
MI5 Director-General Sir Ken McCallum, in a rare and candid public appearance on October 16, 2025, didn’t mince words about the scale of the challenge. “Do Chinese state actors present a U.K. national security threat? The answer is of course yes they do, every day,” he told reporters, according to the Associated Press. He revealed that MI5 had intervened to stop a threat from Beijing as recently as the past week. The gravity of his remarks underscored a broader message: the UK faces “daily” national security threats from China, not just in the abstract, but in the form of real, ongoing operations targeting British interests.
The immediate spark for this renewed scrutiny was the collapse of a criminal case against Christopher Cash, a parliamentary researcher, and academic Christopher Berry. Both men had been charged under the century-old Official Secrets Act, accused of passing intelligence to China that could be “prejudicial to the safety or interests” of the UK. The case, which had been set for trial, was abruptly dropped by the Crown Prosecution Service in September 2025. The decision triggered a formal inquiry by Parliament’s Joint Committee on the National Security Strategy and put Prime Minister Keir Starmer’s government under intense pressure to explain what went wrong.
Director of Public Prosecutions Stephen Parkinson pointed the finger at government officials, saying they had refused to testify under oath that China was a threat to national security during the period of the alleged offenses, which spanned 2021 to 2023. This left prosecutors unable to proceed. Prime Minister Starmer, for his part, has denied any interference, insisting that prosecution decisions are independent and outside the hands of politicians.
To shed light on the government’s assessment, witness statements from Deputy National Security Adviser Matthew Collins were published after the case collapsed. In those statements, Collins described China as “the biggest state-based threat to the U.K.’s economic security” and said Beijing’s espionage activities “harm the interests and security of the U.K.” According to The Guardian, Collins also called China a “highly capable” threat that conducts “large-scale espionage operations” against the UK.
Both accused men have vigorously denied wrongdoing. Christopher Berry stated that he only provided reports for trade links, all based on public information. Christopher Cash, meanwhile, asserted that he never intentionally assisted Chinese intelligence. The Chinese Embassy in London was quick to respond, calling the allegations “pure fabrication and malicious slander” and stating, “China never interferes in other countries’ internal affairs.”
For MI5, the collapse of the case was a bitter pill to swallow. “Of course I am frustrated when opportunities to prosecute national security-threatening activity are not followed through for whatever reason,” Sir Ken McCallum admitted, but he emphasized that prosecution decisions lie outside MI5’s remit. He characterized Britain’s relationship with China as a “complex” mix of risk and opportunity, and stressed that MI5 agents “detect and deal, robustly, with activity threatening U.K. national security.”
This latest episode comes amid a broader escalation of warnings from British intelligence about Beijing’s covert activities. Parliament’s Intelligence and Security Committee had already labeled China a “strategic threat” in 2023, citing cyberespionage, technology theft, and covert interference in British public life. According to BBC News, MI5 has seen a 35% increase in the number of people under investigation for espionage in the past year, a sign of the growing scale and sophistication of state-based threats.
China is not the only country in MI5’s crosshairs. In his annual speech outlining major threats to the UK, McCallum painted a stark picture: Britain faces “multiple overlapping threats on an unprecedented scale” from both terror groups and hostile states. He named China as one of the “big three” state threats, alongside a more reckless Russia and Iran. “State threats are escalating,” he warned, noting that Russia and Iran are increasingly using “ugly methods,” including “surveillance, sabotage, arson or physical violence.”
McCallum alleged that Russia, in particular, is “committed to causing havoc and destruction,” with MI5 and police disrupting a steady stream of surveillance plots targeting individuals considered enemies of the Russian regime. Tehran, too, has been accused of plotting to injure and kill its enemies on British soil, with more than 20 “potentially lethal Iran-backed plots” disrupted in the past twelve months.
The threat from terrorism remains acute as well. The UK’s official terror threat level stands at “substantial,” meaning an attack is likely. Since 2020, MI5 has disrupted 19 late-stage attack plots, with suspects increasingly younger—one in five of those arrested last year were under the age of 17. The motivations behind these plots are diverse, ranging from al-Qaida and Islamic State-inspired extremism to far-right ideology and what McCallum described as a “messy stew of motivations bred in squalid corners of the internet.”
Amid these challenges, the UK is grappling with how to balance the risks and rewards of engagement with China. Starmer’s center-left Labour government has tried cautiously to reset ties with Beijing after years of frosty relations over spying allegations, human rights concerns, China’s support for Russia in the Ukraine war, and a crackdown on civil liberties in Hong Kong. The latest spying controversy erupted just as British officials were considering China’s application to build a massive new embassy near the Tower of London—a project that, if approved, would create the largest diplomatic complex in Europe. Critics say the scale and central location of the proposed embassy bring heightened risks of spying and sabotage. In response to these concerns, the government has postponed the deadline for a final decision on the embassy from October 21 to December 10.
As if these threats weren’t enough, MI5 is also keeping a wary eye on new dangers posed by emerging technologies. McCallum highlighted the risks from artificial intelligence, warning, “Artificial intelligence may never ‘mean’ us harm. But it would be reckless to ignore the potential for it to cause harm.”
The collapse of the China spy case has left many questions unanswered and exposed the delicate balancing act at the heart of British security policy. With state threats on the rise and the machinery of justice under scrutiny, the UK faces a daunting task: defending its interests in a world where espionage, sabotage, and technological disruption are daily realities.
