The River Cherwell carves its way through a broad, deep valley that runs north to south, starting a few miles above the market town of Banbury and continuing down as far as the university city of Oxford, bending and twisting, meeting up sometimes with the Oxford Canal and parting company again as they reach the city outskirts. It is joined by Sor Brook and the River Swere from the west near Adderbury, and the River Ray from the east at Islip. After...