UK Terror Threat Level Downgraded

The terror threat level for the UK has been reduced from severe to substantial, Home Secretary Theresa May has announced.

However, a terrorist attack still remains a strong possibility and may well occur without further warning, she warned.

Mrs May said: "The change in the threat level to substantial does not mean the overall threat has gone away - there remains a real and serious threat against the United Kingdom and I would ask the public to remain vigilant."

There are five levels of threat, ranging from low, meaning an attack is unlikely, to critical, when an attack is expected imminently.

The Home Secretary said: "The decision to change the threat level is taken by JTAC (the Joint Terrorism Analysis Centre) independently of ministers and is based on the very latest intelligence, considering factors such as capability, intent and timescale."

The terror threat level was first made public on August 1, 2006, and was set at severe.

Just nine days later it was raised to critical following a series of arrests over an alleged plot to blow up a transatlantic aircraft, but was once again lowered to severe the week after.

The threat was last increased to critical in June 2007, following an attack on Glasgow Airport in which a car loaded with explosive canisters was driven at the entrance to the terminal. The day before, two bombs were discovered at central London locations and disarmed.

The level is under constant review and often changes quickly in response to events.

The threat from dissident Republican and Loyalist terrorists in Northern Ireland was increased to substantial in September last year, meaning an attack was a "strong possibility".

It followed a warning from the head of the MI5 that dissident Irish republicans could attempt to mount a wave of terrorist attacks on the British mainland.

Scotland Yard chief Sir Paul Stephenson also urged the public to remain vigilent days after the world's most wanted man, Osama bin Laden, was killed in a US operation in Pakistan.

Sir Paul said: "Osama bin Laden led an organisation which is responsible for the injury and death of thousands of people worldwide in the name of an extreme and perverted ideology, committed to the use of terror and murder to achieve their aims.

"However, one man's death does not mark the end of an ideology and we must remain alert to the continuing threat from al Qaeda, its affiliates and those acting alone."