threat level
© flickr/billypalooza
Britain has lowered the threat level from international terrorism less than a year after the last attempted attack.

The level has been reduced from "severe," meaning an attack in highly likely, to "substantial" meaning an attack is a strong possibility, but the Home Secretary stressed that a terrorist attack might occur without further warning.

The threat, which is at the third level of a five point scale, is now at the same level as the threat from Irish terrorism on mainland Britain.

Theresa May, the Home Secretary, said: "This means that a terrorist attack is a strong possibility and might well occur without further warning.

"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."

The decision to change the threat level is taken by the Joint Terrorism Analysis Centre, part of MI5, independently of ministers and is based on the latest intelligence.

Security around the Olympic Games next year is being planned on the basis that the level will return to "severe" for the event.

The last time the level was reduced to "substantial" was in July 2009 but it was put back up six months later after the attempt by Umar Farouq Abdulmutallab to blow himself up on a trans-Atlantic plane using explosives in his underpants.

The last attempted attack in Britain was in October last year when intelligence foiled an attempt by al-Qaeda in the Arabian Peninsular to blow up an aircraft using a bomb in a printer cartridge that was found at East Midlands airport.

The threat level, which was not published at the time, was also lowered in the weeks before the July 7 attacks in 2005.

It has hit "critical" in the wake of the July 7 bombings, the attempt to blow up trans-Atlantic airliners using bombs in soft drinks bottles, and the London and Glasgow car bombings.

The threat from dissident Irish terrorists was published for the first time in September last year, when it was raised to "substantial" in the face of increased capabilities by terrorists in Northern Ireland. It was already at "severe" in Northern Ireland.