Britain’s domestic security service, MI5, is facing what its director general calls a “new era” marked by a surge in both terrorism and state-backed threats, with the scale and variety of dangers now described as more complex than at any point since the September 11 attacks. In a wide-ranging annual address delivered in London on October 16, 2025, Sir Ken McCallum, MI5’s Director General, laid out the daunting landscape of threats confronting the United Kingdom—ranging from child radicalization to sophisticated espionage by global adversaries.
According to BBC and ITV News, McCallum revealed that MI5 is currently contending with near-record volumes of terror investigations and a rapidly escalating risk from hostile states, notably Russia, China, and Iran. “My teams are routinely uncovering attempts by state actors to commission surveillance, sabotage, arson or physical violence,” McCallum said, underscoring the daily reality of national security work in 2025.
Perhaps most striking was the 35% increase in the number of individuals under investigation for threatening the state compared to the previous year—a figure that signals the scale of the challenge. Since 2020, MI5 and police have disrupted 19 late-stage attack plots and intervened in “many hundreds of developing threats,” McCallum noted. The terrorist threat, he explained, has shifted over the years, moving from large, complex networks to smaller groups and lone actors, often radicalized online or through personal networks. “The aggregate scale of the terrorist threat remains huge,” he said, emphasizing the relentless pace and evolving nature of the threat landscape.
One particularly worrying trend is the involvement of minors in extremist activity. “A concerning number of minors are appearing in national security investigations,” McCallum stated. One in five of the 232 terrorism arrests in the UK last year involved children under 17, a statistic that brings with it “complexities” unique to dealing with vulnerable young people. Recognizing the need for a different approach, MI5 announced the creation of a new, multi-agency Interventions Centre of Expertise, designed to support youth who may be on a path toward extremist violence. This center, to be housed within London’s Counter Terrorism Operations Centre, will manage threats involving adolescents, mental ill-health, and other complex risks.
State threats have also become more pronounced and diverse. McCallum made clear that Chinese state actors, in particular, present a daily national security threat to the UK. He revealed that MI5 had intervened operationally to disrupt Chinese activity of national security concern as recently as the past week. “When it comes to China, the UK needs to defend itself resolutely against security threats and seize the opportunities that demonstrably serve our nation,” McCallum declared. The agency’s vigilance includes countering cyber espionage, clandestine technology transfer, and attempts to lure UK academic experts into sharing sensitive knowledge. The director general was careful, however, to avoid being drawn into the political debate surrounding the collapse of a recent China spy case, which was dropped by the Crown Prosecution Service due to insufficient evidence. He did, however, express frustration: “I am frustrated when opportunities to prosecute national security-threatening activity are not followed through for whatever reason.”
Russia and Iran were also singled out for their increasingly aggressive tactics. “Anyone watching the news can see that Russia is committed to causing havoc and destruction,” McCallum said, referencing not only cyber attacks across Europe but also the use of “proxy” actors—such as Bulgarian nationals—motivated by money or the thrill of espionage. He warned that these individuals are viewed as disposable by their handlers: “When you’re caught, you’ll be abandoned.”
Iran’s “autocratic regime” has prompted MI5 to expand its counter-Iran operations significantly over the past year. The agency has tracked more than 20 potentially lethal Iran-backed plots in the last 12 months alone, according to McCallum. These efforts, he said, are part of a broader strategy to counter state threats that now include espionage not just against government agencies but also Parliament, universities, and critical infrastructure.
Amid these external threats, the specter of international terrorism remains ever-present. McCallum warned that groups such as al-Qaeda and Islamic State are “once again becoming more ambitious” and are exploiting instability overseas to gain firmer footholds. The director general explained that MI5’s focus is now primarily on individuals or small cells, rather than the larger networks that characterized past threats. This shift, he argued, reflects both a change in terrorist tactics and improvements in the agency’s ability to disrupt more complex plots before they reach fruition.
McCallum’s speech was shaped by two recent and significant events: the deadly attack on a Manchester synagogue earlier in October, which left two Jewish people dead, and the aforementioned collapse of the China spy case. He began his remarks with a message of condolence: “My deepest sympathies to those bereaved, injured and affected” by the synagogue attack, according to BBC reporting. The tragedy served as a somber reminder that, despite the best efforts of security services, total security remains elusive in an open, democratic society.
Accountability and oversight were also discussed candidly. McCallum acknowledged that MI5 had been “justly criticised” by the courts in relation to false evidence given by the agency in three separate cases. “I want to affirm, on record, the importance MI5 attaches to accountability and oversight,” he stated. “Part of why MI5 exists is to defend our national way of life—a way of life which includes the checks and balances of rigorous independent oversight.”
Looking ahead, McCallum addressed the double-edged sword of technological advancement. He noted that while Artificial Intelligence (AI) offers “immense benefits,” it would be “reckless to ignore the potential for it to cause harm.” The agency is keenly aware of the risks posed by new technologies, both as tools for security and as potential vulnerabilities to be exploited by hostile actors.
The director general concluded his address with a heartfelt tribute to the people behind the scenes at MI5. “I am so proud of the talented, selfless, often courageous MI5 people who show up, day after day, night after night, year after year, to take on these threats. They give their all.” In the face of unprecedented challenges, he maintained, MI5’s mission remains clear: to protect the UK’s national security while upholding the values of a free and open society.
As Britain navigates this “new era” of security threats, the message from MI5 is one of vigilance, adaptability, and a steadfast commitment to both safety and democratic principles. The dangers may be evolving, but so too are the tools and determination of those tasked with keeping the country safe.
