Twenty-five years have passed since the morning that changed the world, and the man now tasked with protecting the United Kingdom from its enemies is asking the nation to look forward rather than back. Sir Ken McCallum, the director-general of MI5, has marked the anniversary of the September 11 attacks by delivering a stark and deeply personal warning: the threats facing Britain today are fundamentally different from those that emerged in the aftermath of 2001, and the country must evolve or risk being caught unprepared. In a reflective piece published in the Independent, Sir McCallum described the current security landscape as presenting “the worst of both worlds.” This is not a simple return to the old certainties of the Cold War, nor is it a continuation of the post-9/11 era of Islamist terrorism. Instead, it is a strange and unsettling hybrid. On one side, there are powerful, hostile states once again flexing their muscles, engaging in espionage, sabotage, and covert influence. On the other, there remain the persistent, unpredictable threats from terrorist groups and individuals who have adapted to the digital age. The MI5 chief’s message is one of relentless adaptation, a call for security to be treated as a shared national endeavour, and a plea to remember the victims of 9/11 by building the defences of tomorrow rather than admiring those of yesterday. It is a sobering reflection from a man who has spent two decades inside the Security Service, and it arrives at a moment when the certainties of the past seem more fragile than ever.
To illustrate the strange new reality, Sir Ken reached back to an evocative metaphor from the immediate post-Cold War era. In the early 1990s, after the collapse of the Soviet Union, CIA director James Woolsey spoke of the West having “slain a large dragon” but now finding itself facing a “bewildering variety of poisonous snakes.” That image captured the optimism and anxiety of the time: the great, monolithic enemy was gone, but a host of smaller, more unpredictable dangers had slithered out from the undergrowth. Now, Sir Ken argues, with a nod to the counterinsurgency expert David Kilcullen, the situation has become even more complicated. In his book The Dragons and Snakes: How the Rest Learned to Fight the West, Kilcullen warned that the West would eventually have to confront both at once. And that is precisely where we now find ourselves. “Dragons are back, but snakes persist,” Sir Ken wrote. The “dragons” are the resurgent nation-states that pose a strategic threat through cyber-attacks, disinformation, espionage, and the targeting of critical infrastructure. The “snakes” are the terrorist networks and lone actors who remain a constant, lower-level danger. The problem is that these two categories are not separate. They overlap, learn from each other, and sometimes even cooperate. A hostile state might use a terrorist group as a proxy, or a terrorist might adopt the techniques of a state-sponsored cyber unit. This is the “worst of both worlds,” and it demands a response that is as flexible and multifaceted as the threat itself. Sir Ken’s use of the metaphor is not merely academic; it is a way of helping the public understand that the old playbooks no longer apply.
There is, however, some good news buried within the warning. Sir Ken acknowledged that the terrorist threat posed by Al-Qaida, the organisation that perpetrated the 9/11 attacks, is now a mere “fraction” of what it was twenty-five years ago. He expressed pride in the work that MI5 and its partners have done to dismantle Al-Qaida’s capabilities, disrupt its plots, and prevent another attack on the scale of those that killed nearly three thousand people in New York, Washington, and Pennsylvania. But he was quick to insist that this success must not breed complacency. The fact that one enemy has been diminished does not mean the battle is over; it simply means the enemy has changed shape. New terrorist groups have emerged, old ones have mutated, and the methods of attack have evolved. The threat is no longer about hijacked aeroplanes flown into skyscrapers; it is about cyber-attacks on hospitals, disinformation campaigns designed to tear apart social cohesion, and small-scale attacks using vehicles or knives that are difficult to predict and prevent. In this environment, Sir Ken argued, the UK cannot afford to rely on the defences it built in the years after 9/11. “We must resist the temptation to admire the defences we built yesterday and instead build the ones we will need tomorrow,” he wrote. That is a powerful and humbling statement. It acknowledges that the security services did an extraordinary job in the wake of 9/11, but it also recognises that those efforts were tailored to a specific threat that has now receded. The next twenty-five years will require a different kind of vigilance, one that is more agile, more imaginative, and more willing to embrace new technologies and new partnerships.
Central to this vision is the idea that security cannot be left to the security services alone. Sir Ken called for a “shared national endeavour,” a phrase that carries real weight in an age of growing polarisation and distrust. He noted that foreign policy is “harder than many commentators allow,” a gentle rebuke to those who imagine that complex international problems have simple solutions. But his main point was more domestic: many of the systems that are now under threat are no longer owned by the state. He cited recent attacks on synagogues as an example of British “assets” in peril, and he pointed out that the critical infrastructure of the country—its energy grids, its financial networks, its communications systems—is increasingly in private hands. This creates a new challenge for MI5 and its partner agencies. In the past, protecting the nation meant guarding government buildings, military bases, and other official sites. Today, it means working with private companies, community groups, and individual citizens to secure a vast and interconnected landscape. It means convincing business leaders that they have a role to play in national security, not just because it is good for their bottom line, but because it is good for the country. And it means asking ordinary people to be more aware, more resilient, and more willing to report suspicious activity. This is not an easy message to deliver in a society that is often sceptical of authority and protective of civil liberties. But Sir Ken’s argument is that the alternative is far worse: a nation that is vulnerable because it refused to accept that security is a collective responsibility.
The personal dimension of Sir Ken’s message is what makes it so compelling. “The horrors of 9/11 will never leave me,” he wrote, and for a man who has spent his entire adult life in the world of intelligence and counter-terrorism, those words are not empty rhetoric. He was not the director-general of MI5 in 2001, but he was already serving in the Security Service, and he witnessed firsthand the aftershocks of that terrible day. He saw the fear, the uncertainty, and the determination that followed the attacks. He also saw the cost of failure and the importance of getting things right. Now, a quarter of a century later, he says that what sits with him every day is MI5’s “perpetual responsibility to keep adapting, at even greater pace, as we seek to deepen the UK’s resilience—now to both dragons and snakes.” That sense of duty is rooted in a belief that the victims of 9/11 are owed more than memorials and moments of silence. They are owed “preparation, resilience and the courage to adapt.” This is a striking way to frame the anniversary. It moves the focus away from the past and toward the future, away from mourning and toward action. It is a reminder that the best way to honour the dead is to ensure that their sacrifice was not in vain, and that the world they died in is one we are determined to make safer. Sir Ken’s language is measured and professional, but beneath it there is an unmistakable emotional weight—a recognition that the decisions made in the coming years will determine whether the next generation faces a world of greater danger or greater safety.
In the end, this is a story about change and continuity. The threats that emerged after the fall of the Cold War and the attacks of 9/11 have not disappeared; they have evolved and multiplied. The dragons have returned, and the snakes are still with us. Sir Ken McCallum’s warning is that the UK must be prepared to face both simultaneously, without losing sight of the values that make it worth defending. He is not predicting doom, nor is he offering false comfort. He is simply stating the truth as he sees it, from the perspective of a man who has spent his life studying the darkest corners of human behaviour. The message is aimed at politicians, at the public, and at his own organisation. It is a call for humility in the face of uncertainty, for courage in the face of danger, and for unity in the face of division. It is also a call to remember that security is not a static achievement but a continuous process. The defences that were built after 9/11 were remarkable, but they were built for a world that no longer exists. The task now is to build the defences for the world that is coming into being, a world of artificial intelligence, climate change, great power rivalry, and persistent, adaptable terrorism. It is a daunting task, but Sir Ken seems determined to meet it. And if his words have the desired effect, the rest of the nation will be determined too. As he himself put it, the horrors of 9/11 will never leave him. But neither, it seems, will the resolve to keep adapting, keep learning, and keep fighting for a safer future.
