Inchgarvie Island, In the 15th c. James IV built a castle on this island to fortify its position, between 1519 and 1671 it operated as a state prison. In 1580, by order of the Privy Council, it was a place of exile for plague victims. Charles II fortified the island in 1651 to oppose Oliver Cromwell, but after his defeat these defences fell into disrepair.