The sealing of Magna Carta is also popularly associated with Magna Carta Island, on the opposite (east) bank of the Thames. It has also sometimes been associated with the nearby Ankerwycke Yew. These and their surrounding landscape of floodplain and parkland may once have formed an integral part of Runnymede, as the river has occasionally changed its course here. Ankerwycke and the ruins of the 12th-century Priory of St Mary's were both acquired by the National Trust in 1998. As the Thames forms the county boundary at this point, these areas now lie in Berkshire.