G.B. England. Buckinghamshire. Runnymede. The ruins of Ankerwycke (or Ankerwyke) St Mary's Benedictine Priory lie a few miles south-east of Windsor, in a field on the bank of the Thames opposite Runnymede. This 12th century priory was thought to be the meeting place of the Witan Council and the place where the Magna Carta was sealed by King John in the presence of his barons and bishops. 2015