I think this is a millstone, left behind long ago in the Abbey Grounds.
According to the Cotswold Archaeological Trust report, Cirencester: Town & Landscape (1994), six water-driven mills are recorded in Cirencester in the Medieval period. Most of them (certainly Barton Mill, New Mill and Langley Mill) were at some time fulling mills. [It doesn't take too much to imagine worsted cloth pegged out on tenterhooks along the Gumstool Brook!]
1. Barton Mill
2. The Abbey Mill, used by the monks of the Abbey; situated on the Gunstool Brook just within the abbey precinct in Gosditch Street [see plaque].
3. St Mary's or New Mill, [built by Abbot Blake about 1530]
4. Langley's Mill
5. A fifth mill site identified at the foot of Cecily hill.
6. Brain's Mill in Gloucester Street. This mill belonged to the Abbot in the 13th century and was probably used to grind oak bark for tanning.
Here is a map published in the CAHS Newsletter which show the mills and related watercourses:
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| Map from CAHS Newsletter 2011 |