High Quality Content by WIKIPEDIA articles! Richard of Conisburgh, 3rd Earl of Cambridge (c. 20 July 1385 – 5 August 1415) was the second son of Edmund of Langley, 1st Duke of York, and Isabella of Castile. At the age of thirty he was beheaded for his part in the Southampton plot, a conspiracy against King Henry V. He was the father of Richard Plantagenet, 3rd Duke of York, and the grandfather of King Edward IV and King Richard III.