Debate on the origin of the `shelly boulder clays` of Great Britain and Ireland has gone full circle from the mid-nineteenth century view of the `great submergence`, through later ascription to terrestrial ice crossing sea areas while incorporating marine shells, to current controversy on their possible glaciomarine status. A case is made that the terrestrial and glaciomarine views are not mutually exclusive. Glaciomarine deposits are found at relatively low elevations at and within the immediate coastal hinterland. Amino acid ratios from both their in situ and derived marine shells, together with AMS radiocarbon ages on contemporary foraminifera, indicate two marine transgressions of oxygen isotope stage 5 age and immediately before, during and after the Last Glacial Maximum (23-19 ka). These allow inferences to be drawn, in different parts of GB and Ireland, that pre-LGM ice was both more extensive and thicker than during the LGM, when thinner and low gradient ice streams occurred, with extensive unglaciated areas upstream from the LGM ice limit. New amino acid data are presented from England, Ireland, Wales and Scotland.