About two miles to the west of the town of Dunstable, in Bedfordshire, lies the village of Totternhoe, and between the two a spur of the Chiltern hills juts out in a north-westerly direction into the surrounding countryside. It forms a steep-sided promontory about a mile and a half long and from the top of the ridge there are commanding views over the area around.

Through the middle of the ridge runs a stratum of chalk which has become compacted hard enough to be used as a building stone, often referred to as Tottenhoe Clunch, though in strict geological terms the word Clunch should be applied only to a form of chalk stone found in Cambridgeshire.

The Totternhoe bed lies within a band of chalk which extends north-eastwards across the country from Dorset, in the south-west, through Hampshire, Wiltshire, Berkshire, Bedfordshire and East Anglia, up to the north Norfolk coast, with spurs off to the south forming the North and South Downs. The stone itself is a sedimentary limestone, laid down millions of years ago when England was still under the ocean. As the tides ebbed and flowed the currents deposited material resulting from the erosion of older rocks which had been temporarily exposed when the level of the sea fell for a time. It consisted of pebbles of phosphate, fine, gritty particles of glauconite, phosphatic grains and shell fragments, and as the deposits built up the lower layers became compacted by the weight of those above, becoming hard enough to to be used for building.

The stratum of stone here lies sandwiched between a layer of grey chalk above and one of soft chalk marl below. Because so much chalk has been removed from the surface in the 20th century it is difficult for us now to assess the depth of the original overburden, but Victorian geologists estimated in the 1880s that the roof of the quarries was about 21.5m to 24.7m (70 to 80 ft) below the surface of the ground.l Though there are other places in which ·smaller outcrops or deposits of the stone have been identified, locally at Edlesborough and in Hertfordshire at Hitchin and Arlesey, for instance, it is at Totternhoe that the layer reaches its maximum thickness, varying from approximately 2.5m (8 ft) to S.2m (17 ft).