Terrorism Levels

I was listening to Radio 4's PM programme with Eddie Mair yesterday, and I was amused by a story which was attempting to decipher the new five levels of threat from Terrorism that the Government will be publishing.

The problem seems that the Government has decided to issue the five levels of threat, but no explanation as to what they mean. So if today is a "Severe" day, and tomorrow was a "Critical" day, what should I do differenty? Perhaps I should avoid public transport, or even leaving the house? The problem is that the spokesman that was on the show couldn't actually define the five levels and the public's expected associated behaviour.

Useful or pointless? We'll see.