He became involved with the latest rebellion of the Percies in the north, and raised an army with Richard le Scrope, Archbishop of York. Deserted by the Earl of Northumberland, Norfolk and Scrope were brought to book on Shipton Moor by a large royal army under John of Lancaster and the Earl of Westmorland. Seeking a parley, they were arrested as soon as they disbanded their followers. When Chief Justice Sir William Gascoigne refused to pass sentence upon them before they were tried by their peers, Henry IV had both Norfolk and Scrope summarily beheaded in York on 8 June 1405. This conspiracy is the main historical context for Shakespeare's Henry IV, Part 2, and the execution is described with the words "Some guard these traitors to the block of death, / Treason's true bed and yielder up of breath."
He was buried in the Church of the Greyfriars in York. His head was displayed for two months on a pike at Bootham Bar before it was taken down and reunited with the body. Legend had it that the head retained the freshness of life.[2]
^Tait, James (1894). "Thomas Mowbray (1386–1405)". In Lee, Sidney (ed.). Dictionary of National Biography (volume 39 ed.). Smith, Elder & Co. pp. 236–237.
Alison Weir, Britain's Royal Family: A Complete Genealogy (London, U.K.: The Bodley Head, 1999), and
G.E. Cokayne; with Vicary Gibbs, H.A. Doubleday, Geoffrey H. White, Duncan Warrand and Lord Howard de Walden, editors, The Complete Peerage of England, Scotland, Ireland, Great Britain and the United Kingdom, Extant, Extinct or Dormant, new ed., 13 volumes in 14 (1910–1959; reprint in 6 volumes, Gloucester, U.K.: Alan Sutton Publishing, 2000), volume VII