The Romans built a small fort there called "Blestium", but few people lived in the area after the Romans left. Eventually, the Normans built a castle by the River Monnow, after they conquered England in 1066. Monmouth grew in the Middle Ages, with a priory church, and a market street (now called Monnow Street). This street ran between the castle and a fortified bridge across the river, which is the only fortified bridge of its type in Britain. King Henry V of England was born in Monmouth Castle in 1387, but the castle itself was mostly knocked down after the Civil War in the seventeenth century.