Hull Castle was constructed to defend the east side of the town of Kingston upon Hull against a possible French attack; it was also intended to ensure the loyalty of the population, who had taken part in a revolt against the King in 1536.
Henry had visited Hull in late 1541 and had observed that, although the town had strong walls to the north and west, it lacked adequate defences in the event of an attack from the east, while the harbour was only protected by a "little round brick tower".
Henry issued orders for the existing town defences to be repaired and renovated but, before the work could commence, he changed his mind and issued fresh instructions in early 1542.
John Rogers, a military engineer previously stationed in Guînes, was brought back to England to construct a major system of defences on the east bank of the River Humber, comprising a central castle linked to two large blockhouses.

The design of the new defences was probably carried out by Rogers and resembled his earlier work near Calais, although the King probably also made some decisions on the project personally.
Sir Richard Long and Michael Stanhope were instructed to oversee the construction of the defences, with Thomas Aldred acting as the project's paymaster and William Reynolds in the role of master mason.
Initial estimates suggested that 530 workers would be needed, including masons, carpenters and plumbers, but more may have been required in practice.
Some of the building materials were taken from monastic institutions, which had recently dissolved by Henry; stone and lead was taken from the nearby Meaux Abbey, further stone from the friaries in Hull and probably also from St Mary's Church in Hull, which had recently collapsed.
At least some of the bricks needed were made in a series of ten kilns beside the site itself.
The land needed for the buildings had been seized during the dissolution of the monasteries.
By December 1543, £21,056 had been spent on the project.

The castle was rectangular, with brick and stone foundations and a brick superstructure.
It had two large, curved bastions containing chambers on the west and east ends, and a three-storey rectangular keep in the middle, 66 by 50 feet (20 by 15 m) across, set within an inner courtyard.
The outer wall was 19 feet (5.8 m) thick and contained a gallery and ports for hand-guns, and supported two tiers of artillery.
A moat ran around the outside of the castle.
The two-storey tall blockhouses were also built from brick and stone, and each had a square central tower and entrance at the rear, and three curved bastions to the front and sides.
Their walls were 16 feet (4.9 m) thick, sloped so as to deflect incoming fire, and supported two tiers of guns; the interiors were partitioned, to reduce the risk of explosions damaging the entire fortification.
The use of bastions adopted some features from the Italian-style of defences then popular on the continent, but their design was imperfect and failed to provide flanking cover or interlink with the neighbouring defences.
A crenellated curtain wall, approximately 900 metres (3,000 ft) long and 12 feet (3.7 m) high, linked the blockhouses and castle, with a wet moat on the eastward side.
Hull Castle was constructed to defend the east side of the town of Kingston upon Hull against a possible French attack; it was also intended to ensure the loyalty of the population, who had taken part in a revolt against the King in 1536. Henry had visited Hull in late 1541 and had observed that, although the town had strong walls to the north and west, it lacked adequate defences in the event of an attack from the east, while the harbour was only protected by a "little round brick tower". Henry issued orders for the existing town defences to be repaired and renovated but, before the work could commence, he changed his mind and issued fresh instructions in early 1542. John Rogers, a military engineer previously stationed in Guînes, was brought back to England to construct a major system of defences on the east bank of the River Humber, comprising a central castle linked to two large blockhouses. 
The design of the new defences was probably carried out by Rogers and resembled his earlier work near Calais, although the King probably also made some decisions on the project personally. Sir Richard Long and Michael Stanhope were instructed to oversee the construction of the defences, with Thomas Aldred acting as the project's paymaster and William Reynolds in the role of master mason. Initial estimates suggested that 530 workers would be needed, including masons, carpenters and plumbers, but more may have been required in practice. Some of the building materials were taken from monastic institutions, which had recently dissolved by Henry; stone and lead was taken from the nearby Meaux Abbey, further stone from the friaries in Hull and probably also from St Mary's Church in Hull, which had recently collapsed. At least some of the bricks needed were made in a series of ten kilns beside the site itself. The land needed for the buildings had been seized during the dissolution of the monasteries. By December 1543, £21,056 had been spent on the project.
The castle was rectangular, with brick and stone foundations and a brick superstructure. It had two large, curved bastions containing chambers on the west and east ends, and a three-storey rectangular keep in the middle, 66 by 50 feet (20 by 15 m) across, set within an inner courtyard. The outer wall was 19 feet (5.8 m) thick and contained a gallery and ports for hand-guns, and supported two tiers of artillery. A moat ran around the outside of the castle. The two-storey tall blockhouses were also built from brick and stone, and each had a square central tower and entrance at the rear, and three curved bastions to the front and sides. Their walls were 16 feet (4.9 m) thick, sloped so as to deflect incoming fire, and supported two tiers of guns; the interiors were partitioned, to reduce the risk of explosions damaging the entire fortification. The use of bastions adopted some features from the Italian-style of defences then popular on the continent, but their design was imperfect and failed to provide flanking cover or interlink with the neighbouring defences. A crenellated curtain wall, approximately 900 metres (3,000 ft) long and 12 feet (3.7 m) high, linked the blockhouses and castle, with a wet moat on the eastward side.
Hull Castle