Edain: the Northumbrian comments in the thread on English attitudes to folk music. The name Logres bounced up from my subconscious and I wondered about its derivation. I've a fair amount of stuff on the Arthurian period - mythical and historical - but it had never occurred to me to ask where the word came from. It seems (from the above help and others) that it is first found in the 12th Century texts, and where it is used as a poetical name for England - or sometimes the part of Britain that became England.
But so far the Leicester comment is the only one to suggest a derivation. There may be other hints in the use of it to describe London - given that London existed 1000 years before Roman Londinium this might be possible, but I'm not sure how solid such a suggestion might be. (As in a choice between not very and very not very.)