On December 20, 2025, the United Kingdom’s intelligence community found itself at the center of an extraordinary and deeply consequential inquiry. An urgent appeal was issued to all current and former MI5 staff, seeking information regarding false evidence presented by the service to three courts in a high-profile neo-Nazi spy case involving an informant known as Agent X. This renewed call for cooperation, as reported by the BBC, reflects the ongoing complexities and unexpected twists that have come to define this long-running saga—one that not only implicates the nation’s security apparatus but also raises profound questions about institutional accountability, transparency, and the enduring challenges of intelligence work.
The case first gained public attention in February 2025, when BBC investigations revealed that MI5 had lied to courts while defending its handling of Agent X, a misogynistic state informant who, among other serious offenses, attacked his girlfriend with a machete. The scandal deepened when it emerged that MI5 had also misled its own regulator, the Investigatory Powers Commissioner, Sir Brian Leveson. According to the BBC, MI5 had disclosed Agent X’s status in phone calls to a journalist, attempting to dissuade further investigation, while simultaneously insisting in court that it had adhered to its policy of not confirming or denying informants’ identities. This duplicity was only exposed after the journalist produced a recording of one such call, forcing MI5 to confront the reality of its actions.
Prime Minister Sir Keir Starmer responded swiftly. In September 2025, he ordered a comprehensive investigation after both the High Court and the Investigatory Powers Tribunal rejected MI5’s explanations about the false evidence. The gravity of the situation was underscored by the fact that MI5 had also misled Sir Brian Leveson himself, whose office is now leading the new inquiry. In a letter updating the prime minister, the attorney general, and the home secretary, Sir Brian revealed that his team had “asked that a message be disseminated to all current MI5 staff,” inviting anyone with potentially relevant information to come forward. “I am grateful for MI5’s prompt and constructive engagement to achieve this,” he wrote, but also noted, with some exasperation, that “relevant material continues to be identified,” even four years after the case began and more than three years after his inspectors first examined the Agent X situation.
This persistent emergence of new information is, in Sir Brian’s words, “surprising.” Yet, as intelligence experts and historians know all too well, such phenomena are not uncommon in the labyrinthine world of espionage. Layers of secrecy, compartmentalization, and the sheer volume of classified records can obscure the truth for years—sometimes even decades. As BBC coverage and other analyses have pointed out, the process of reconstructing the narrative of a sensitive intelligence operation is often protracted and complex, requiring the review of vast archives, interviews with numerous current and former personnel, and the cross-referencing of disparate pieces of information that may have been overlooked or deemed insignificant in earlier phases of the investigation.
The current investigation is being led by Sir John Goldring, the Deputy Investigatory Powers Commissioner, who, according to Sir Brian’s update, has already interviewed 36 people over the past five weeks. These interviews have included “current and former staff of the intelligence services,” as well as BBC staff, government lawyers, and barristers representing MI5. The inquiry has uncovered “additional lines of inquiry” after obtaining material that went beyond what was disclosed in the three original court cases. The final report is not expected before March 2026, a timeline that reflects both the scope of the investigation and the seriousness with which the authorities are treating the matter.
What’s at stake in this inquiry goes far beyond the fate of Agent X or the reputations of individual MI5 officers. As the BBC notes, the investigation aims to identify systemic vulnerabilities within the intelligence community and to implement reforms that will prevent similar incidents in the future. The government’s determination to address national security concerns thoroughly is evident in the breadth of the appeal, which targets not only those with direct involvement but also anyone with indirect knowledge—no matter how minor or seemingly insignificant their observations might be. The leadership of the inquiry believes that even small pieces of information, perhaps forgotten or dismissed at the time, could prove pivotal in piecing together a complete and accurate account of what transpired.
The stakes are high for MI5 as an institution. In July 2025, a panel of senior high court judges criticized previous internal investigations, stating that they “suffer from serious procedural deficiencies” and that “we cannot rely on their conclusions.” The judges ruled that it would be “premature” to decide on contempt of court proceedings against any MI5 officers before the new investigation was complete. This pointed rebuke underscored the need for a more rigorous and transparent process—one that could restore public trust in the intelligence community’s ability to police itself.
For its part, MI5’s leadership has pledged full cooperation. Director General Sir Ken McCallum issued what the BBC described as an “unreserved apology” for the false evidence, and stated unequivocally that the service would support the new inquiry. Two official inquiries had previously absolved MI5 officers of deliberate wrongdoing, attributing the false evidence to mistakes and poor memories. However, these findings failed to satisfy the courts or the public, leading to the current, more comprehensive investigation.
Beyond the immediate legal and procedural questions, the inquiry also highlights the critical role of human intelligence in national security. As emphasized by both the BBC and government statements, the knowledge, recollections, and insights of individual intelligence professionals are irreplaceable. While technology and automated systems play an ever-larger role in modern espionage and counter-espionage, it is often the observations and memories of people—sometimes decades old—that provide the missing context or crucial link in a complex case. Recognizing this, the inquiry has guaranteed a confidential and secure process for staff to come forward, protecting their anonymity and the sensitivity of any information they provide.
The broader implications of the case are clear. The ongoing investigation serves as a stark reminder of the persistent and evolving threats posed by espionage, both foreign and domestic, to critical national institutions and sensitive government operations. It also demonstrates the UK’s resolve to address breaches of national security, no matter how long ago they may have occurred. By sending a public appeal for information, the authorities are signaling to potential adversaries that the passage of time will not diminish their determination to uncover the truth and protect state secrets.
When the final report is delivered in 2026, its findings and recommendations are expected to inform future policy and operational adjustments not only within MI5 but potentially across the entire UK intelligence community. Such systemic reviews are vital for adapting to new threats, refining security protocols, and ensuring that lessons from the past are translated into stronger protections for the future. The process, though arduous, reflects a profound commitment to accountability and the enduring importance of national security in an uncertain world.
