Base line figure

At last I have found and visited this famous site (Well, famous to some).  This cannon, 3/4 of which is buried under the ground, marks one end of the original base-line measured by General Roy in the late 1700s.  This  provided the core measurement which enabled the whole of the United Kingdom to be surveyed and as a consequence we have the wonderful maps of the Ordnance Survey today. Originally the line was plotted across empty heathland.  London AIrport now sits on the site as do a few thousand houses!.  And finding it gave me the chance to have a break from a lovely 2 year old's party!