The Head of MI5, Sir Ken McCallum, has warned that Britain faces a more complex national security environment than it did before the 9/11 attacks, urging government, businesses, academia and the public to treat national security as a shared responsibility.
Sir Ken McCallum has warned that Britain remains vulnerable to mass-casualty terrorist attacks as it confronts a growing and increasingly sophisticated threat from hostile states, The Independent reports.
According to Sir Ken McCallum, “the MI5 I lead in 2026 contends with a threat landscape markedly different to 2001’s.”
“Sadly, mass-casualty terrorist ambition endures, but the terrorist threat now sits alongside strategic national security threats posed by capable States.”
Sir Ken McCallum
Sir Ken described the current situation as “the worst of both worlds,” arguing that the threats that dominated the post-Cold War period have returned while extremist threats have persisted.
His warning comes as Britain’s national terrorism threat level remains at severe, the second-highest category, indicating that an attack is highly likely.
According to Sir Ken, the response to al-Qaeda following the 9/11 attacks demonstrated that determined international action could significantly reduce the capabilities of terrorist organisations.
He argued that al-Qaeda had to be dismantled after continuing to plan mass-casualty attacks around the world.
“Al-Qaeda had to be not just taken on, but taken down. Al-Qaeda remains a threat today, but its capabilities are a fraction of 2001’s. That rollback was not inevitable; it was forced.”
Sir Ken McCallum
However, Sir Ken cautioned against allowing that success to create complacency, stating that, “we must resist the temptation to admire the defences we built yesterday and instead build the ones we will need tomorrow.”
“Contending with rising State-backed aggression, whether sabotage subcontracted to criminals, or covert interference in our democracy, or destructive cyber attacks on power stations demands new laws as well as new tradecraft.”
Sir Ken McCallum
Russia has previously been accused of using a range of hostile activities against UK, including cyber operations, interference and state-sponsored violence, making the wider threat environment increasingly difficult to address through traditional security structures alone.
Sir Ken stated that Britain cannot afford to wait for another major crisis before determining who is responsible for responding to vulnerabilities.
According to him, a major difference between the security environment of 2001 and today, Sir Ken argued, is the extent to which critical systems and infrastructure are controlled by private companies.
“In 2026, unlike 2001, many of the assets, systems and services under threat sit in private sector hands. This means many of the most critical decisions will be taken not in COBR but in boardrooms.”
Sir Ken McCallum
He therefore called for closer cooperation between government, businesses and academia to identify vulnerabilities and ensure that the country can respond quickly when crises occur.
“We need a new team of teams, preserving an open economy but cooperating across government, industry and academia, to close vulnerabilities and enable swift coherent action when crises hit.”
Sir Ken McCallum
In the midst of increased geopolitical tensions, Britain and its allies are reevaluating their strategy for national resilience, which coincides with Sir Ken’s intervention.
He contended that the entire nation must contribute to safeguarding vital systems and getting ready for potential shocks, rather than seeing national security as the exclusive purview of the military and intelligence services.
“This is my call to arms after 25 years: government, business, academia, and the public must treat national security not as the specialist concern of a handful of agencies, but as a shared national endeavour.”
Sir Ken McCallum
Remembering 9/11
Sir Ken’s warning was issued as countries around the world marked 25 years since the September 11 attacks, which killed 2,977 people, excluding the 19 hijackers.
On September 11, 2001, four passenger planes were hijacked by members of al-Qaeda. Two were flown into the World Trade Center’s Twin Towers in New York, while another struck the Pentagon near Washington, DC.
The fourth aircraft, United Airlines Flight 93, crashed into a field near Shanksville, Pennsylvania, after passengers attempted to regain control of the plane.
The attacks killed passengers and crew aboard all four aircraft, as well as thousands of people in New York and at the Pentagon. Among those killed were 441 first responders in New York, the largest loss of emergency personnel in US history.
Thousands more people were injured or later developed illnesses linked to exposure to the toxic debris generated by the attacks.
For Sir Ken, however, remembrance must be accompanied by preparation.
“We owe the victims of 9/11 and those who will otherwise become the victims of tomorrow’s attack something more than remembrance. We owe them preparation, resilience and the courage to adapt before the next shock arrives.”
Sir Ken McCallum
His message is that the lessons learned from 9/11 must be used beyond the battle against terrorism. As threats change, Britain must improve its ability to withstand attacks on its infrastructure, institutions, economy, and democratic systems.
The MI5 chief’s concern is no longer whether Britain will suffer another major security shock, but whether the country will be prepared when it does.
READ ALSO: Stop Setting Up Offices in Your Entities, Mahama Tells State Board Chairs
