Who is Henry Stafford, Duke of Buckingham from The Princes in the Tower and what is their importance?

Henry Stafford, Duke of Buckingham, was a prominent nobleman. He also had a claim in the line of succession. Henry was married to Catherine Wydville, the Queen's sister, and he became Richard of Gloucester's ally after Edward IV's death. Buckingham supported Richard's reign without question until Richard told him of his intent to kill the Princes in the Tower. When Richard learned that Buckingham was conspiring against him, he had him executed.