Well we finally got our own American style terrorist threat level and it's already gone all the way up to 4:
The government today made public its official assessment of the threat of a terrorist attack, warning that it is "severe" - meaning an attack is highly likely. The five-level categorisation is published for the first time on the MI5 website, and is one degree short of the most severe rating - "critical", which means an attack is "imminent".
Actually we've been on SEVERE for almost a whole year already. So no imminent attacks then. Of course on the morning of July 7th the (then non public) terror threat level had recently been knocked down a notch to SUBSTANTIAL. After that it seems that SEVERE will be the default setting for some time. No one is going to take the gamble of reducing the terror threat level anytime soon...
Speaking of gambling, the new warning system is part of a larger governmental counter-terrorist strategy that is, believe it or not, code-named CONTEST.
Those settings in full are Low, Moderate, Substantial, Severe and
Run For The Hills Critical.
From Mi5's handy THE THREATS page if you click Threat Levels in the UK the first thing you see is a photo of the Home Secretary. You probably don't want to read too much into that...