The observed effect is largely an urban-rural divide.
Yet the South East (in a functional sense, including London, most of Essex, etc) is the most thoroughly urbanised region of the country. Of course many of its inhabitants would dispute this (despite throughly urban lifestyles, occupations... and many people actually working in the centre of London for Christssake etc) but then there's a very strong national delusion about such things in Britain.
The key thing isn't so much urban/rural, but industrial/non-industrial.
Though the reason for this has changed; in the 19th century the most important electoral cleavage was religion, and so solidly Anglican counties in the South East were also solidly Tory.