prelate, bishop of London (1522–30) and of Durham (1530–52 and 1553–59), who was a leading conservative in the age of the English Reformation. He wrote an excellent arithmetic textbook, De arte supputandi libri quattuor (1522) and a treatise on the Eucharist in which he defended the Roman Catholic doctrine.

Born illegitimate, Tunstall studied law at Oxford, Cambridge, and Padua universities. In 1508–09 he became chancellor to William Warham, archbishop of Canterbury, and from 1514 he advanced rapidly in Thomas (later Cardinal) Wolsey's service, being employed particularly on diplomatic negotiations abroad. In the Reformation he reluctantly broke with Rome and firmly opposed doctrinal innovation, yet remained in Henry VIII's favour, while his European reputation made his eventual submission politically valuable. In 1537–38 he served as president of the Council of the North.

Imprisoned and deprived under Edward VI (though initially a member of the council of regency), he was reinstated by Mary but refused the oath of supremacy under Elizabeth and was again deprived (1559).