The large rectangular building, 68ft. by 23ft. (internal measurements ) forms the basement of the original Ramsey Abbey House which Sir Oliver Cromwell (the Protectors Uncle) came to live in after selling Hinchingbrooke House to Sir Sydney Montague in 1627.
This 13th century building has always been a mystery as to what it was originally used for, so far it was thought to have been a refectory or a Lady Chapel. The recent paper written by CAM ARC, Cambridgeshire County Council 2008, have come up with an idea from they're model C theory that it more likely represents an infirmary chapel or a chapter house.
The Chapter house theory to me looks reasonably promising because recently I have found a photo of a Chapter house at Canterbury which contains many architectural similarities to the Ramsey building above. Below are the two photos to give some idea of the likenesses. Although the one at Canterbury is much more ornate.