The work was funded by a studentship (GT 4/94/322) awarded to JAH by the Natural Environment Research Council. We thank H. Sloane (NIGL) for isotopic analysis, R. Janssen (Naturmuseum Senckenberg) for provision of modern North Sea specimens, A. Weller (BGS) for information on mollusc distributions in North Sea sediments, G. O'Hare (University of Derby) for useful discussion of the relationship between oceanic and atmospheric temperature, and LOIS for funding radiocarbon dating. This is LOIS publication number 825.