Legend has it that the stone originally stood on the opposite side of the road and was considerably taller. The present stone is merely the top of the original stone which was hacked off when building and road works were carried out, leaving the rest of the stone under the ground (below the current pavement level). Apparently, whoever did this considered the stone just a roman mile marker. There are also stories of tall pre-roman walls that lie buried under the urban conurbation of central london (although I find this harder to believe).
Sadly, the london stone does look rather sad and is quite disappointing, although I would love to know what really lies under the modern level in that area.
Whilst on the subject of London stones, what about the King Lyle stone in Kingston, and Dick Whittington's stone in Archway?
johan