Earlier in the year I stayed at the Lodge in Avebury and Andy Burnham told me about this stone. I work in Harrow and Andy, who is from close by, told me about the local sites. It took me a while to find this stone and kept asking colleagues who live locally if they knew of it. finally I was pointed to a restaurant in the Harrow Weald area which used to be a pub called the Hare (probably after the stone). I am also told that the name Harrow (famous for it's public school) derives from 'Hare'. Apparently Harrow Hill itself, where the school is, was sacred and used for worship but I am not sure how my colleagues come to know this.
I have yet to find out more about this stone and it's more famous neighbour (the Weald Stone, OS ref: TQW150908) ) a mile or so down the hill. It looks like it has been broken in the past and I was wondering if it was perhaps part of an old tomb or burial mound.
I believe that further up the hill (the Harrow Weald hill, not Harrow-on-the-Hill) is an old earthworks but this is going to take longer than a lunch break to discover and so will it have to wait for another day.
If and when I find out more about this stone I will add information here.
I had been wondering if "Hare" and "Harrow" had the same etymology and looked up Harrow in John Field's book 'Place Names of Great Britain and Ireland'. The entry for Harrow-on-the-Hill says it means "Heathen Shrine on the Hill".