[chimprich]

London is not a great counter-example because it has been a major settlement for at least a couple of millennia.

[falsedan]

No it hasn't, Londinium was abandoned when the Romans vacated Great Britian.

[TheCoelacanth]

The Roman settlement was, but London as a whole was only abandoned briefly if at all. There was a major Anglo-Saxon settlement outside the Roman walls in what is now Covent Gardens and the Strand definitely in the 6th century and possibly in the 5th. The Roman settlement started declining in population towards the beginning of the 5th century.