The original invasion threat passed, but the castle was reinforced in 1558, due to fresh concerns of a French attack.[21] Around 1570, the main bastions were filled with earth, probably to allow heavier guns to be mounted on them, and Queen Elizabeth I inspected the castle in 1573.[22] The defences along the coast were mobilised in 1588 in response to the threat posed by the Spanish armada and were probably kept ready for action throughout the rest of Elizabeth's reign.[23]