Complex sentence: St.Andrew's Castle is the remains of a defensive structure dating to the reign of King Henry VIII and was built in around 1543 as part of the Device Forts, being a chain of coastal fortifications designed to defend the solent from French naval attack.
Split into simpler sentences: St.Andrew's Castle is all that remains of a defensive structure dating to the reign of King Henry VIII. It was built around 1543 as part of the Device Forts, a chain of coastal fortifications designed to defend the solent from French naval attack.