LondonEveningStandard The festive period would be a prime time for terrorists to strike because of its symbolic importance to the UK and its allies, says former British Army officer and security expert Mike Yardley.

"After being seen to come off badly in Afghanistan, the network's chiefs will be keen to prove its potency abroad," the historian and military expert says.

"Defences are liable to be down over the Christmas holiday, making it an ideal choice for terrorists."

He said an attack may include "exotic" weapons, including the so-called dirty bomb, which uses conventional means to spread large doses of radiation.

American spies in Afghanistan recently found evidence Bin Laden and his al-Qaida network had made strides towards producing the device.

The warning comes after anti-terrorist officers swooped on a cargo ship in the English Channel in what Scotland Yard described as a "major security operation".

Mr Yardley said: "What we have seen is another example of how vulnerable the country remains.

"The al-Qaida network proved on September 11 that it is capable of highly sophisticated strategy and will almost certainly have been plotting a new attack since then."

Britain would be a likely target because of its support in the war against the Taliban, he said. "It is very likely that we will see more of these operations in the next few days."

-- Anonymous, December 21, 2001