John Cavendish is descended from Robert de Gernon who lived during the rein of Henry I and who gave a large amount of property to the Abbey of Gloucester.
His son, also called Robert de Gernon, of Grimston Hall, Suffolk, married the heiress of John Potton of Cavendish and obtained a landed estate in the lordship and manor of Cavendish. In consequence, his four sons exchanged their father's name for that of the estate each inherited. John was the eldest of the brothers.
One of his brothers, Roger Cavendish, was the ancestor of Thomas Cavendish known as "The Navigator".
Sir John Cavendish became a lawyer and rose to Lord Chief Justice of the King's Bench. He was also elected Chancellor of the University of Cambridge.
As Chief Justice he was obliged to suppress the Peasants' Revolt in 1381.
His son, John Cavendish, had killed Wat Tyler, one of the leaders of the Revolt, for which he was knighted at Smithfield and received a large grant of money from the King.
As a result of this, his father, Sir John Cavendish, was then pursued by the peasants, and he made it to St. Mary's Church, Cavendish, where he pleaded sanctuary by grasping the handle of the church door. This was to no avail, however, and he was taken to the market place at Bury St. Edmunds and beheaded by a lynch mob led by Jack Straw. He died on June 15, 1381, and is buried in Bury St. Edmunds.
St. Mary's Church, Cavendish, benefited from a large bequest made by Sir John and had its chancel refurbished.
Sir John's great-grandsons are William Cavendish (3rd husband of Bess of Hardwick) and George Cavendish, William's brother and Cardinal Thomas Wolsey's biographer.