Actually I think the Mordor/London analogy holds up well in any case. JRRT was unashamedly provincial in outlook, and there's evidence for his distrust of the centralising tendencies of Whitehall bureaucracy, with all that that implied for loss of cultural identity in other regions of England. This fear of being taken over, of being 'swamped' may strike a chord with, for example, the average American or French view of Washington or Paris respectively - part of the reason for LOTR's continuing popularity perhaps?
Were the Danes 'evil'? I don't think so either (and nor did JRRT as you say), but nor were they the cuddly bunnies of modern revisionism. They undoubtedly had a nice line in 'shock and awe' tactics, but then as the old proverb says 'You can't make an omelette without killing several million Russians'
.. Their contemporary Christian opponents certainly depicted them as evil - 'The Scourge of God' no less - but then they would, wouldn't they?
It doesn't make any difference to my identification of the historical situation in Alfred's time with the basic geopolitical structure of LOTR. There is no allegory here. LOTR is a fantasy: Gondor is NOT Wessex, Aragorn's story is NOT the same as Alfred the Great's, and as has been forcefully pointed out on other threads Orcs are NOT Vikings.
It seems absurd to accuse JRRT of a lack of imagination, but it's rather unfortunate that he ended up with this particular geography for Middle Earth. He could have placed his 'evil force of destruction' at any point of the compass he chose, but by putting it in the east and south he appears to put LOTR firmly into the whole history of threats to Western European civilisation from that quarter - from the Goths and Huns, Arabs, Mongols, Turks et al right down to Nazi Germany and Soviet Russia. This has been a gift to allegory-hunters ever since the book was written.
Note that the Silmarillion never seems to get plagued by these kinds of historical analogies, for the good reason that the forces of evil are stuck up in the far north. A Chinese or Indian reader might feel the cultural resonance of a northern invasion (after the Mongol and Mughal invasions respectively), but it's not easy to come up with a european parallel. The clearest ones I can think of - a northern force bringing physical destruction and cultural annihilation to an artistically advanced, culturally, racially and politically diverse south - would be the Albigensian Crusade against southern France in the mid13th century, or it's Iberian contemporary the
Reconquista of Christian Spain against the Moors. JRRT would have hated both these comparisons, of course, since they cast Catholic Christianity in the role of Morgoth.
