Most speculation about this is that what people are witnessing is the ghost of Judith Langham.

"Other reports tell of a phantom hitch Hiker thumbing a lift and getting picked up by the Lower Bell pub on the same road and putting the world to rights all the way to Maidstone... before vanishing right from the seat."
http://www.bbc.co.uk/southerncounties/content/articles/2005/08/15/strange_south_a229_feature.shtml