The keep was added to the castle in the reign of Henry I, and in the reign of Elizabeth I, when the Spanish Armada was expected, it was surrounded by additional fortifications by Sir George Carey, who had been appointed Governor of the Isle of Wight in 1583. Carey later commissioned the Italian engineer Federigo Giambelli (or Genebelli) to make more substantial improvements to the defences. Starting in 1597, Giambelli constructed a modern trace Italienne fortification, a squat rampart and ditch supported at intervals by powerful bastions, which completely surrounded the old castle and bailey. The new fortification was mostly completed by 1600 at the cost of £4,000.[5]
