MI5 chief warns Britain must 'build defences' against radical Islamic threats in unprecedented intervention

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Sir Ken McCallum warned the UK must now contend with 'dragons' and 'snakes' on the global stage

The Director General of MI5 has warned Britain must "build defences" against radical Islamic threats in an unprecedented intervention.

Sir Ken McCallum warned the global terror landscape is more complex than it was 25 years ago, when the world witnessed the horror of 9/11.

As well as the threat of Islamic extremism persisting, the MI5 chief said, the West also contends with state-level threats.

Writing in The Independent, he said: "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."

Referencing the US's former CIA director James Woolsey, who after the Cold War said the West had defeated a "large dragon", Sir Ken said in today's world, we now contend with both "dragons" and "snakes".

"Dragons" being state-actors, such as Russia and China, whose capabilities to spy, disrupt and cause terror are significant.

Also continuing to rear its head are smaller "snakes", non-state actors, such as radical Islamic extremists, who have less resources than nations, but can be sponsored by them to commit acts of terror.

Sir Ken wrote: "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."

The UK's terror threat level is currently defined as "severe", which means an attack is highly likely.

This designation was raised on April 30 after two Jewish men were stabbed in Golders Green, north London.

Before then, the terror threat level had remained unchanged for four years.

Terrorism has existed for thousands of years; however, its severity has worsened in more recent memory.

On 9/11, 25 years ago today, 2,977 people, including 67 British citizens, died in America in what is widely considered the worst terror attack the world has ever seen.

Sir Ken recalled how someone in MI5 said "Osama Bin Laden" as they watched the Twin Towers fall, and what proceeded was the necessary "taking down" of Al-Qaeda, in a "gargantuan multinational effort".

He wrote: "Al-Qaeda had to be not just taken on, but taken down. A gargantuan multinational effort, powerfully spearheaded by the US, devised new capabilities to dismantle the core of the organisation in Pakistan’s federally administered tribal areas, into which it had been pushed by the Afghan campaign.

"It worked. Al-Qaeda remains a threat today, but its capabilities are a fraction of 2001’s. That rolling back was not inevitable; it was forced."

Despite the West's success in destroying Al-Qaeda, Sir Ken warned the West must not become complacent as new, more complex threats develop.

While radical Islamic extremism remains a threat, the "dragons" must be approached with a "whole nation response", said the MI5 chief, rather than relying solely on specialist security services.

He wrote: "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.

"Russia has used the full spectrum of attacks that he refers to against the UK in the last 15 years as well as state-sponsored murder.

"We cannot wait for the next shock to discover who owns the vulnerability, who has the authority to act, or who was supposed to pick up the phone."

The reality of threat is a matter or "when" not "if" for Sir Ken, requiring a significant level of planning that not only sits with public entities, but also private.

"In 2026, unlike 2001, many of the assets, systems and services under threat sit in private sector hands," he wrote.

"This means many of the most critical decisions will be taken not in Cobra meetings but in boardrooms."

Sir Ken concluded by paying tribute to the victims of the 9/11 attack, saying we "owe" them and "those who will otherwise become the victims of tomorrow's attack... something more than remembrance".