In 1522 a great chain was ordered to keep enemy ships from entering the harbour. It was stretched from Point to Blockhouse at Gosport. The Castle by the South Sea`s buildings were commenced in 1538. It was the building of the Castle that gave birth to a new word "Southsea". The building of the Castle was followed by the erection of two small circular forts on the shore, one on the site of Lumps Fort and the other at Eastney.

In 1545 the English Fleet was lying at anchor at Spithead. On 18th July news was received that a French fleet, numbering 200 vessels was off of the Isle of Wight and advancing. They were brought to almost within gunshot of the English ships. The Mary Rose had her ports open for action, the guns were run out, and in consequence of the calm, had not been secured properly. The breeze rose suddenly, and the vessel heeled slightly, the windward tier of guns then slipped across the deck and as the vessel tipped further the ports were depressed below the water line. The ship instantly filled and carried down with her almost all on board.

The meeting of the fleets gave us the National Anthem, for the British watchword was "God Save King Henry" and the ringing answer came: "Long to reign over us".