Geoffrey's Revenge is a flaming bag of bungle fingers (or indeed a bungle fist) found upon ones doorstep, that can only be dowsed with the merry stampings of the unitiated. Although not exclusive to this, It is most likely found upon the doorstep of Thames telivison staff circa 1992.
'Maude! Maude! Call a Bobby! There's a massive Geoffrey's Revenge on the door step and I fear my slippers can't take it!" - 1992 Thames Television executive, circa 2005