 Complete the following phrase:  In the 15th century a 5-storey keep was built by Bishop Cameron, this was later extended with additional fortifications and buildings, constructed by later bishops. Archbishop Beaton added a large corner tower, and Archbishop Dunbar built a round-towered gatehouse in 1544. The central keep served as the residence of the bishop, and was called the Bishops Palace. The castle played a role in the many political battles during the 16th century, including the 