The area has been inhabited for thousands of years. There were several prehistoric burial mounds on Cock Marsh which were excavated in the 19th century and the largest stone axe ever found in Britain was one of 10,000 that has been dug up in nearby Furze Platt. The Roman road called the Camlet Way is reckoned to have crossed the Thames at Sashes Island, now cut by Cookham Lock, on its way from St. Albans to Silchester. By the 8th century there was an Anglo-Saxon abbey in Cookham and one of the later abbesses was Cynethryth, widow of King Offa of Mercia. It became the centre of a power struggle between Mercia and Wessex. Later King Alfred made Sashes Island one of his burhs to help defend against Viking invaders. There was a royal palace here where the Witan met in 997.