By 550 AD London was engulfed in the Saxon advance. London disappeared into the Dark Ages. The Saxons were congenitally averse to urban living; more, they considered the stone buildings of the Roman-British cities to be work of Giants - and so best avoided. London fell into ruin. An Anglo-Saxon poet, wandering around the remains of an unknown abandoned British city, versed his impressions of such a place:

WELL WROUGHT THIS WALL: Wierds [fates] broke it. 

The stronghold burst…

Snapped rooftrees, towers fallen,

the work of the Giants, the stonesmiths,

mouldereth,

Rime scoureth gatetowers

rime on mortar

Shattered the showershields, roofs ruined,

age under-ate them.

And the wielders and wrights?

Earthgrips hold them - gone, long gone,

fast in gravesgrasp while fifty fathers

and sons have passed

Wall stood, grey lichen, red stone, kings fell often,

stood under storm, high arch crashed - 

stands yet the wall stone, hacked by weapons,

by the files grim-ground…

…shown the old skilled work

…sank to loam crust…