Bridges over the river were created in Saxon times at Nottingham at least (and for a time just north of Newark at Cromwell, although it is not known how long that bridge site lasted), and formed major centres of trade and military importance. King Edward fortified the Nottingham bridge in 920, while a notable battle took place at Burton's bridge in 1322, and another in 1643. The medieval bridges of Burton and Nottingham survived relatively intact until the 1860s, when both were replaced and demolished. The central arches of the medieval Swarkestone bridge were knocked out by the great flood of 1795 and rebuilt, but the bridge's more rural location allowed large portions of the medieval bridge to survive and remain in use today. Crossing a wide flood plain, the bridge is almost long, a laborious project to allow flood waters to pass under it. At Newark, the last bridge on the Trent until modern times, the bridge was rebuilt in 1775. At least one other medieval attempt was made to bridge the Trent near Wilden at Hemington, but this was gone long before the end of the Middle Ages. The complex of three bridges provides evidence of attempts to keep a crossing open over slightly more than two hundred years from 1097, with three bridges constructed on the same site but felled by scouring, floods and course migration of the river to the south eroding the bridgehead. The bridge was probably gone by around 1311 when nearby Wilden ferry, near Shardlow was first recorded, and the site thereafter went without a bridge until Cavendish Bridge opened around 1760. As no archive sources record that the Hemington bridge existed, there may have been other medieval bridge projects now forgotten. (Until the late 18th century, a long period of stagnation for economic and technical reasons limited the number of bridges over the Trent; it has been noted that relatively few bridges were constructed in England on new sites anywhere between around 1250–1300 and 1750.) Cavendish Bridge was itself damaged beyond repair by a flood in March 1947, requiring a temporary Bailey bridge to be used until a new concrete span was constructed in 1957.