is located on the eastern side of the River Yar estuary on the Isle of Wight and was built by Henry VIII in around 1547 to protect the island from invasion by the French. The French had landed on the Isle of Wight briefly a couple of years earlier and it was probably this event that Henry has reacting to. It is one of a series of gun-forts that Henry had built to protect the whole of the south coast. Hurst Castle, another of Henry's gun-forts is located on the other side of the Solent. Like other gun-forts built at the time, Yarmouth Castle was designed not as a residence but as a platform to hold large guns, but its shape is completely different. While most of the other gun-forts had a circular central tower, Yarmouth Castle has a square tower with 100 feet long sides.