These posts date from the mid 19th century, when the City of London Corporation imposed a tax on coal (and other goods) entering the metropolitan area. The posts stand at points on the boundary of that area - though the locations chosen seem pretty arbitrary.
Uploaded to Geograph by Stefan Czapski on 3 March 2013
Photo © Stefan Czapski, 3 March 2013. Licensed for reuse under this Creative Commons licence