Palaeomagnetic, chemical and pollen analyses have been carried out on cores 6 m long from the SW basin of Loch Shiel, Sootland. A marine regression in one core is dated at 4200 Cl4 years BP. Palaeomagnetic declination and inclination variations in the limnic gyttja are interpreted as reliable records of ancient geomagnetic field changes. Comparison with 4 other British limnic palaeomagnetic sites indicates that systematic errors in Cl4 age determinations have been caused in many of the sites by inwash of old soils and peats. The inwash effect is suggested to have been more pronounced and to have started significantly earlier in England than previously documented. Palaeomagnetic direction correlations and transference of Cl4 age determinations from the palaeomagnetic master curve described, can help overcome these dating difficulties.