When the Romans left in the 5th century, the area was settled by Saxons. In the 9th century, Watling Street became the frontier between the kingdom of Wessex and the Danelaw, so Towcester became a frontier town. Edward the Elder fortified Towcester in 917. In the 11th century, the Normans built a motte and bailey castle on the site. Bury Mount are the remains of the fortification and is a scheduled ancient monument. It was renovated in 2008 with an access ramp added and explanatory plaques added.