The British security services on Tuesday made public for the first time their assessment of the probability of a terrorist attack, telling Britons they face a "severe" threat, meaning that an attack is "highly likely."
Under a new system introduced in an effort to make the intelligence services seem more open, the threat level appeared on several Web sites, including www.intelligence.gov.uk, which is run by the espionage and counterterrorism establishment, and www.mi5.gov.uk, run by the domestic security service.
The level of peril facing Britons has been contentious since last year, when the security services lowered the threat assessment two months before the bombings of July 7 last year, in which four bombers killed 52 passengers on the London transport system.
"Threat levels are designed to give a broad indication of the likelihood of a terrorist attack," the intelligence.gov.uk site said. "They are based on the assessment of a range of factors including current intelligence, recent events and what is known about terrorist intentions and capabilities. This information may well be incomplete and decisions about the appropriate security response are made with this in mind."
Unlike the previous secret grading system, which offered seven levels of threat, the new system has been simplified to five, from "low" to "critical," meaning an attack is expected imminently.
"Severe" is the second-highest level, but the Web site did not say what kind of attack was thought likely. The assessment is roughly the same as it has been for a year.
Britain's apparent vulnerability relates to assumptions among intelligence experts that its military presence in Iraq as the US' staunchest ally has made it a target.
Assessing the threat from al-Qaeda, the Web site said, "British and foreign nationals linked to or sympathetic with [al-Qaeda] are known to be present within the [UK]."
The relative openness follows other measures by the intelligence elite to swap its traditional cloak-and-dagger for a web-and-wired modernity. Last October MI6, the secret intelligence service which once denied its own existence, launched a Web site to advertise for recruits.
But that has not satisfied lawmakers, at least those preoccupied with human rights.
A cross-party parliamentary panel known as the Joint Committee on Human Rights took umbrage when Dame Eliza Manningham-Buller, the director general of MI5, refused to be questioned about recent anti-terror legislation.
Her reticence seemed to revive lawmakers' concerns about the quality of British espionage after intelligence reports used to justify the Iraqi invasion in 2003 proved wrong.