died Dec. 14, 1417, London
distinguished soldier and martyred leader of the Lollards, a late medieval English sect derived from the teachings of John Wycliffe. He was an approximate model for 16th-century English dramatic characters, including Shakespeare's Falstaff.
The son of Sir Richard Oldcastle, he fought for England in the Scottish campaign of 1400 and during the Welsh wars gained the friendship of King Henry IV's son Henry, prince of Wales. By his marriage in 1408 to Joan, heiress of John, 3rd Lord Cobham, Oldcastle entered nobility and in 1409 was summoned to the House of Lords as a baron.
In 1413 he was indicted by a convocation, presided over by Archbishop Thomas Arundel of Canterbury, for maintaining both Lollard preachers and their opinions. His amicable relationship with the prince of Wales, now Henry V, earned him special consideration, but he failed to honour the king's appeals to submit and was brought to trial the same year. Unyielding in his views, he was convicted as a heretic but was granted a stay of execution by the king for 40 days and was imprisoned in the Tower of London. Within a month he escaped to find refuge with the Lollard bookseller William Fisher at Smithfield, where he conspired to kidnap the king at Kent while Lollards answered a summons to assemble at St. Giles's Fields, near London, the night of Jan. 9, 1414. The king was warned by his agents, and the small group of Lollards in assembly were captured or dispersed. Oldcastle again escaped, evading capture until November 1417. Parliament then reiterated his condemnation and penalty, and on December 14 he was hanged over a fire that consumed the gallows.
In The Famous Victories of Henry the Fifth, the anonymous source play for Shakespeare's Henry IV, Sir John appears briefly as a friend of Prince Hal (or Henry). Shakespeare kept the name Oldcastle for the first version of his play but later changed it to Falstaff. Shakespeare's Falstaff is considered to be more boisterous than Oldcastle had been in real life.