The fact that this stone is not already on TMA does make me wonder if it’s prehistoric or not. Perhaps someone knows or will give it a look. It’s a scheduled monument, but there’s no information via ‘Magic’. There’s a photo you can enlarge at Celia Haddon’s website. She says it’s a small stone, and was the location of the Hundred’s moot in Anglo Saxon times. It looks an irregular strange shape, and it’s got a hole in it.
A little bit from ‘Notes and Queries’ (June 7th, 1942, p358):
The Kiftsgate stone from which the hundred takes its name is hidden away among bushes in Weston Park, just off the high road which runs from Chipping-Campden to Broadway. Canon Bourne, Vicar of the parish in which Weston Park lies, who died at the end of last century, at a good age, related that he knew an old man years before who recollected George III being proclaimed king at this boundary stone.
H.C. Hill.