East Mersea preserves ancient river channels and their fossil wildlife beside the tidal shore at Cudmore Grove. Early Eocene London Clay underlies much younger deposits containing shells, wood and mammal remains. The Middle Pleistocene channel at Cudmore Grove is distinct from younger hippopotamus-bearing deposits farther west, and both need careful protection. Pleistocene, Eocene, Cliffs and Foreshore, Rating: ♦♦♦♦