Hi Malone, you may well shiver, it looks and smells yukky! That said, the stall where it was sold, Tubby Isaacs, is/was world famous (sort of) - you might enjoy these old photos:-
http://spitalfieldslife.com/2013/06/13/so-long-tubby-isaacs-jellied-eel-stall/
The 'green sauce' you mention is indeed called 'liquor', but it's served with pie and mash, another East End 'delicacy' - it's actually not bad, again, sort of!