A giant picked up this stone to trash a rival’s house with. You can still see his fingermarks in it. On the way there he slipped and dropped it, and it lies where it fell.
This site tells you everything you could wish to know about the history and folklore of the Tibblestone at its 6-ways crossroads.
This story is mentioned in Alfred Watkin's book 'The Old Straight Track'. However I always thought that the giant lived on Dixton Hill and liked to throw rocks into the River Severn but one day he slipped and the stone landed at Teddington