Terror Alert Level: "Severe, High, And Elevated"

Everyday when I sign online one of the first things I see is the terror alert level on my Google homepage. Today, for the first time in a long time, it was at something other than "elevated". For all flights from the UK, the terror alert level is at its highest; "severe," for all commercial flights in general it is at its second highest level; "high," and for everything else it is still in the middle; "elevated."