The pre-Pliocene sub-aereal surface of the London Clay in the Orford area of Suffolk is discussed. It is shown that south of Aldeburgh the slope of the London Clay towards the north must be less than previously thought and that prior to the deposition of the Coralline Crag a major river ran approximately from south to north in the area studied. This river course may help to explain the sudden drop of the London Clay surface north of Aldeburgh which has not been fully accounted for previously.