Britain has seen a credible "terrorist" attack plot about once a year since the September 11 attacks, a worrying pattern as London prepares to host the Olympics, the head of the country's intelligence agency has said.
Jonathan Evans, MI5's director-general, spoke at the mayor of London's annual defence and security lecture on Monday. He said that although the threat level in the United Kingdom is a notch below where it has been for much of the past decade, the risk is still substantial.
"Our assessment is that Britain has experienced a credible terrorist attack plot about once a year since 9/11,'' he said. "The [Olympic] games present an attractive target for our enemies and they will be at the center of the world's attention in a month or so," he said.
"But the games are not an easy target, and the fact that we have disrupted multiple terrorist plots here and abroad in recent years demonstrates that the UK as a whole is not an easy target for terrorism."
Not so long ago, 75 per cent of the terror threats prioritised by MI5 had links to Afghanistan or Pakistan, Evans said. But Britain's efforts, along with those of its international partners, has brought that percentage down to below 50 per cent.
"You could say that we are near to reaching a form of stalemate," said Evans. "They haven't stopped trying but we have got better at stopping them."
But the "terrorist" threat is also widening to include al-Qaeda affiliates in Mali, Yemen, Somalia and parts of the Middle East, he noted.
The 'Arab Spring effect'
Evans also said that although uprisings in the Arab world have brought about radical political changes in some countries, they have also brought fresh opportunities for al-Qaeda affiliates to seek refuge.
"Some are heading home to the Arab world again,'' Evans said.
"And a small number of British would-be jihadis are also making their way to Arab countries to seek training and opportunities for militant activity, as they do in Somalia and Yemen. Some will return to the UK and pose a threat here. This is a new and worrying development."
MI5 has grown since the September 11 attacks in the United States, going from 1,800 to 3,800 staff, some of whom joined after Britain's own homegrown suicide bombings that killed 52 people in 2005.
Since then, several international terror plots have been hatched in the UK, including the 2006 trans-Atlantic airliner plot to down several planes using liquid explosives. A handful of terror trials are also under way.
Evans stressed that other countries, such as Iran, should not be underestimated either. "We have seen in recent months a series of attempted terrorist plots against Israeli interests in India, Azerbaijan and elsewhere," he said.
"So a return to state-sponsored terrorism by Iran or its associates, such as Hezbollah, cannot be ruled out as pressure on the Iranian leadership increases."
And the threat of cyberattacks has recently become more prominent, he said. In one recent case, a major London-listed company incurred revenue losses of $1.2b because of a single attack, Evans said.
He did not elaborate on the company's name or what country was behind the attack.
"What is at stake is not just our government secrets but also the safety and security of our infrastructure, the intellectual property that underpins our future prosperity and the commercially sensitive information that is the lifeblood of our companies and corporations,'' he said.