Complex sentence: Robin of Locksley--an English nobleman who joined Richard the Lionheart, King of England in the Third Crusade--is imprisoned in Jerusalem along with his comrade, Peter Dubois.
Split into simpler sentences: Robin of Locksley was an English nobleman who joined Richard the Lionheart, King of England in the Third Crusade. Locksley is imprisoned in Jerusalem along with his comrade, Peter Dubois.