The Associated Press is reporting that Britain's government reduced its terror alert level on Monday to its lowest level since the July 7, 2005 bombings of the London transport system, but warned that the threat remains serious.
The government did not explain its decision to downgrade the threat from ''severe,'' which Britain's domestic spy agency MI5 describes on its Web site as a ''high likelihood'' of future terror attacks'' to ''substantial,'' which means that such an attack remains a ''strong possibility.''
Britain's Home Office announced the new alert level in a brief e-mail to journalists. It did not detail the reason for the change, saying only that its analysis center makes judgments based on a broad range of factors. ''We still face a real and serious threat from terrorists and the public will notice little difference in the security measures that are in place, and I urge the public to remain vigilant,'' Home Secretary Alan Johnson said in the e-mail.
Britain's five-tiered alert system—which starts at ''Low'' and passes through ''Moderate,'' ''Substantial,'' and ''Severe'' before hitting ''Critical''—is similar to the United States' system of color-coded terrorism advisories, which has been criticized as vague.
Britain's previous, secret alert system, which worked on a slightly different scale, was overhauled and made public after a report showed it had little effect on police preparedness before the London transit bombings, in which four suicide bombers killed 52 people. That investigation also revealed that the alert level had been dropped to ''Substantial'' only two months before the attacks.
The new British alert system made its debut at ''Severe'' and it has largely remained there since, although it briefly rose to ''Critical'' after authorities foiled an alleged plot to blow up North America-bound aircraft in August 2006 and botched car bomb attacks in London and Scotland in June 2007.