Complex sentence: It was begun in 1511 as a home for Edward Stafford, 3rd Duke of Buckingham, and is not a true castle designed to serve as a fortress, but rather an early example of a Tudor country house, with minimal defensive attributes.
Split into simpler sentences: It was begun in 1511 as a home for Edward Stafford, 3rd Duke of Buckingham. It is not a true castle (designed to serve as a fortress), but rather an early example of a Tudor country house, with minimal defensive attributes.