 The confluence of the Thames and Cherwell was the site of early settlements and the River Cherwell marked the boundary between the Dobunni tribe to the west and the Catuvellauni tribe to the east (these were pre-Roman Celtic tribes).In the late 1980s a large Romano-British settlement was excavated on the edge of the village of Ashton Keynes in Wiltshire.In  43, under the Emperor Claudius, the Romans occupied England and, recognising the river's strategic and economic importance, built fortifications along the Thames valley including a major camp at Dorchester.