The church of St Michael was built on top of a large mound, probably in the 13C. The mound is obviously artificial as the site is on the flood plain of the River Itchen and close to its source. It looks like a classic round barrow to me although for obvious reasons the church and graveyard have obliterated any subtle details which could date it.
As is usual, photos can't give an impression of the height but the top of the mound is nearly level with the eaves of the local cottages.
The "Wayfarers Walk" (Hants County Recreation) says that "...the medieval building has endured much restoration work due to continual structural failure".
Revenge of the older Gods?
Hampshire Treasures suggest that the mound is "Celtic", what ever that might mean.