Recent site investigations and research on Chesil Beach, Dorset, have provided new data which help to shed light on the origin of both the Beach and the lagoonal Fleet which is situated to landward. A channel of the order of -26 m is indicated between the Isle of Portland and the mainland. Under much of the Fleet there is a marked break of slope at about -15 m O.D. This is associated with pebbles, cobbles and boulders and takes the form of a storm beach with planation surface to seaward. Overlying this surface are various deposits dating from Pollen Zone VI onward. In the light of these data the surface must, as in the case of those at Orford, Suffolk, be entirely pre-Flandrian. A tentative chronology is given.