Published BGS gravity data of the UK Southern North Sea Basin show the presence of a gravity low trending to the ESE across the northern half of Quadrant 47. Two simplified geological cross-sections have been constructed across this feature with sedimentary structure based upon well information and reflection seismic data. Gravity modelling of these sections demonstrates that the gravity anomaly is unlikely to be produced by the presence of thick, low density sediments. Consequently, the presence of a large, buried granite batholith is postulated. The buoyant influence of such a granite may have exerted considerable tectonic control during the development of the Southern North Sea Basin. In particular, its presence may help to explain the development of the East Midland Shelf, the associated complex fault movements along the Flamborough Head and Dowsing Fault Zones, and the areal distribution and thickness of the Rotliegendes sand.