The Norman Castle
The Castle is likely to have initially been a motte and bailey structure, built of timber and turves with an encircling ditch, it may even have occupied the site of an earlier stronghold. By 1068, in the year of the death of William the Conqueror, it had been rebuilt in stone. It occupied a prominent, strategic position at the head of the estuary formed by the old course of the River Ouse and a branch of the River Nene, these waterways providing good communications with inland centres. The Saxon settlement was located across the Nene in what is now the Old Market area. 
The Castle came under the jurisdiction of the See of Ely from 1215 and subsequently became the venue for Bishop's Courts
It was clearly an important Castle, being visited by Edward I on a number of occasions between 1292 and 1305, with Edward IV visiting in 1469.
However, it is the visit of King John on 12th October 1216 which is particularly memorable as he lost his supply wagons whilst attempting to cross the.estuary. The search for his 'treasure' has continued ever since.
Use as a prison is documented from the late 13th century, when prisoners included the wife of Robert Brus, and in 1315, poor Richard Lambert of Lynn was 'so inhumanly gnawed by toads and venomous vermin that his life was despaired of'
The Castle was repeatedly subjected to flooding, recent excavations show layers of silt deposted by floods. In 1236 it was severely damaged by an 'inundation' but still continued in use. In the 15th century an additional gate was added adjacent to the Church in what is now Museum Square. In 1478 the Norman castle was largely demolished and replaced by a new structure, a palace for the Bishop of Ely, John Morton. It was still of sufficient importance to sustain the position of Constable for a further two hundred years.
Constables of Wisbech Castle
1246 William Justice
1262 Simon de Dullingham
1308 Richard de Halstead
1401 Thomas de Braunstone
1403 Sir John Rochford
1410 Sir John de Colvile
1446 Sir Andrew Hoggard
1476 Sir Thomas Grey
1489 St Thomas Hobard
1531 Thomas Megges
Sir Richard Cromwell
1605 William Chester
1633 Matthias Taylor
Constables were not always as security conscious as they might have been and at times prisoners were allowed to escape. During the tenure of Sir John de Colvile, a French nobleman and prisoner of war, Jeanne de Creichy broke his parole to rejoin the French forces. He explained to King Henry that he would fight any Englishman who accused him of dishonour. The king told him that he would either be taken prisoner again or killed. He fought in the Battle of Agincourt where he was killed along with his brother.
Other Constables too were taken to task for their incompetence.
