Built in 1544, the Castle was part of a series of fortifications constructed by Henry VIII around England’s coasts to protect the country from invaders. Over the centuries, Southsea Castle’s defences were strengthened so that it could continue to protect Portsmouth. In the 19th Century a tunnel was built to defend the Castle moat. Visitors can still enter the tunnel and see how the Castle would have been defended against invaders. For a while it was a military prison. A lighthouse was built in the 1820s, and is still in use by shipping today. In 1960 the Castle left military service. It was acquired by Portsmouth City Council, which restored the Castle to its 19th century appearance.
Southsea is one of the largest of Henry VIII.’s “blockhouse” forts which were erected on the southern coasts about 1538-40, with the forts of Hurst, Calshot, Deal, Sandown, Portland, and others, when he was expecting invasion by the Catholic Powers; it defends the entrance to Portsmouth Harbour, and has been in latter times converted into a strong work. The common in rear of it was the usual camping ground for troops forming the English armies of the Henrys and Edwards, and many expeditions in those times were mustered and disciplined on that ground.
Edward VI. stayed a night in this fort in 1552. In Elizabeth’s reign its garrison consisted of two officers and a master gunner, two “porters”, eleven gunners, and eleven soldiers.
Its capture in 1642 by a party of Parliamentary troops is thus recorded in the Parliamentary Chronicle: “On Saturday, September 2nd, in the night, the Parl. forces took Sousey Castle, which lyes a mile from the town upon the sea sands. The captain of the castle’s name was Challiner, who on Saturday had been to Portsmouth, and in the evening went home to the castle, and his soldiers took horse-loads of provisions, biscuits, meal, and other necessaries for them. They reported that he had more drink in his head than befitted. The taking was thus: Here were about eighty musqueteers and others, that came by night to the walls of the castle, and under their ordnance, and had with them a very good engineer, and thirty-five scaling ladders; and the whole company of the castle were but twelve officers, whereof ours having suddenly and silently scaled the walls, called unto them and advised them what to do, shewing the advantage they had over them, and therefore their danger if they resisted; who seeing the same, immediately yielded the castle to us, whereof our triumph in taking it was plainly heard at two o’clock in the morning into the town; and as soon as they were masters of the castle, they discharged two pieces of the castle ordnance against the town. The town of Portsmouth capitulated the next day”. In the reign of Charles II. this place was surrounded by a star fort, and .was frequently used as a State prison. In 1760 a great portion was destroyed by an accidental explosion of powder. In 1814 the castle was made into a modern fortress, with proper batteries, and covered ways, ditch, glacis and armament. (Castles Of England, Sir James D. Mackenzie, 1896)