The Science and Engineering Research Council recognized the need for a soft clay test bed site in Britain. The agreed specification was for a site of at least five hectares of normally consolidated material with a plasticity index greater than 20% and a thickness greater than 10 m. The paper describes the philosophy behind the selection process and details the feasibility studies undertaken at Brean and Newport on the Severn Estuary, Swale on the Thames Estuary and Bothkennar on the Forth Estuary. As a result of these investigations the Bothkennar site was chosen. The consistency of the Carse Clay deposits in the Forth Estuary is shown to be related to the similar rates of eustatic and isostatic rise in that area between about 8500 and 6500 years BP. The southeast corner of the site has more silt-rich/laminated material, believed to be related to a meander infill. The site level is slightly lower than the immediate hinterland, suggesting the effects of isostatic uplift have been compounded by flood tide erosion, which it is believed has removed the upper part of the original Carse Clay deposits.