What island is part of the Islands of Furness and has a castle that was used as a base by the Yorkist pretender Lambert Simnel in 1487?
Piel Castle: Piel Castle, also known as Fouldry Castle or the Pile of Fouldray, is a castle situated on the south-eastern point of Piel Island, off the coast of the Furness Peninsula in north-west England. Piel Castle:  It was used as a base by the Yorkist pretender Lambert Simnel in 1487, but by 1534 it had fallen into ruin and passed into the hands of the Crown. Piel Island: Piel Island lies half a mile (1 km) off the southern tip of the Furness Peninsula in the administrative county of Cumbria, though historically within Lancashire north of the sands. Piel Island:  It is one of the Islands of Furness.
Piel Island