between 70 and 80 AD the Romans
built a fortress, known as Deva Victrix and consisting of earth
ramparts with a wooden palisade, beside the River Dee. They
reconstructed their defences 20 years later using sandstone.
After the Norman conquest, during the 11th. century, the walls
were extended and the circuit completed about 100 years later.

C U on the email, keith 