The fall of Afghanistan to the Taliban is likely to have “emboldened” so-called lone wolf terrorists in the UK, the director general of MI5 has warned.

Ken McCallum told the BBC that while the terror threat would not change overnight, there could be a “morale boost” for extremists.

“We need to be vigilant for an increase in inspired terrorism,” he said.

A total of 31 late-stage attack plots have been foiled in the UK in the past four years, said Mr McCallum.

That includes six during the pandemic period alone, he added. While they were largely Islamic extremist plots, there were also a “growing number” of attacks planned by extreme right-wing terrorists.

“The terrorist threat to the UK, I am sorry to say, is a real and enduring thing,” he added.

He was speaking to BBC Radio 4’s Today programme on the eve of the 20th anniversary of the September 11 attacks on the US.