LONDON // Britain has seen a credible terrorist attack plot about once a year since the September 11 attacks in 2001, the head of the country's domestic spy agency said.
It is a worrying pattern as security officials brace themselves for an array of threats ahead of next month's Olympics in London.
Although Britain's threat level is currently a notch below what it has been for much of the past decade, it is still listed as "substantial", meaning an attack is a "strong possibility".
"Our assessment is that Britain has experienced a credible terrorist attack plot about once a year since 9/11," said Jonathan Evans, MI5's director general, during a rare public speech to the Lord Mayor's annual defence and security lecture in London.
"The Games present an attractive target for our enemies and they will be at the centre of the world's attention in a month or so," he added. "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.
"You could say we are near to a form of stalemate. They haven't stopped trying but we have got better at stopping them."
Not so long ago, 75 per cent of threats prioritised by MI5 had links to Afghanistan or Pakistan. But international efforts have brought that percentage down to below 50 per cent, Mr Evans said.