Together with two supporting blockhouses, it defended the eastern side of the River Hull, and was constructed by King Henry VIII to protect against attack from France as part of his Device programme in 1542.

After the restoration of Charles II, the buildings were neglected until the King redeveloped the eastern defences of Hull in 1681, creating a larger fortification called the Citadel.

Hull Castle was built as a consequence of international tensions between England, France and the Holy Roman Empire in the final years of the reign of King Henry VIII.

Traditionally the Crown had left coastal defences to local lords and communities, only taking a modest role in building and maintaining fortifications, and while France and the Empire remained in conflict, maritime raids were common but an actual invasion of England seemed unlikely.

[1] Modest defences based around simple blockhouses and towers existed in the south-west and along the Sussex coast, with a few more impressive works in the north of England, but in general the fortifications were limited in scale.

[6] In response, Henry issued an order, called a "device", in 1539, giving instructions for the "defence of the realm in time of invasion" and the construction of forts along the English coastline.

[10] 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".

[12] 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.

[13] 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.

[20] 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.

[23] 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.

[24] After the construction, Sir Richard Long and Michael Stanhope were placed in command of the castle and blockhouses; the initial garrison may have been substantial, costing around £1,000 a year, but this was mostly demobilised at the end of 1542.

[32] The Earl of Sussex complained in 1569 that they were in need of repair, and a 1576 survey stated that their gun platforms were in poor condition and that the ditches had become clogged with earth, while coastal erosion had undermined the South Blockhouse.

[36] The ground-floor of the South Blockhouse was often used for this purpose; the conditions were particularly poor, with contemporary accounts noting that the quarters "have been overflowed with water at high tide, so that they walked, the earth was so raw and moist that their shoes would cleave to the ground".

The town of Hull argued that since the revenues of £50 granted in 1553 were insufficient to maintain these defences, they should be allowed to use royal customs duties to assist in the work, particularly in protecting the east bank of the river from erosion.

[31] A commission was established to examine the defences and concluded that the position of the castle meant that it was militarily useless, and as a consequence it had not been garrisoned or maintained for many years, resulting in it falling into total disrepair.

[31] Around 1627, Robert Morton, the mayor of Hull, had an additional rectangular earthwork battery of four guns constructed around the south blockhouse to defend the estuary against a potential Spanish and French invasion threat.

[45] In 1643, the mayor, Thomas Raikes, and the Parliamentarians in Hull concluded that the governor, Sir John Hotham, was planning to seize the castle and the wider town for the King.

[47] The artillery exchanges during the sieges and the activities of the garrisons had caused considerable damage, and at the end of the conflict the military Governor of Hull ordered repairs.

[67] The foundations of the Citadel, which had been too substantial to dismantle in the 19th century, were uncovered during urban regeneration works in 1987, and archaeological digs have occurred on both the castle and the South Blockhouse sites.