In 1290 Oct 30, Petrus Episcopus Exon (Bishop Peter Quinel) was granted, by Edward I, (In year 18 of his reign) a Royal licence to crenellate his Exeter house (Exeter Episcopal Palace and Cathedral Close)

"Licence for Peter, bishop of Exeter, to strengthen with a wall and to crenellate his Exeter house (mansum)."

Granted at Clipstone,

Licences to crenellate granted to Bishop Peter Quinel in 1290 and Bishop Walter Stapledon in 1322.

Original source is

• Calendar of Patent Rolls (1281-92) p393

(In fact, the original source given is usually a transcription/translation of what are precious medieval documents not readily availably. It should be noted that these transcription/translations often date to the nineteenth or early twentieth centuries and that unwitting bias of transcribers may affect the translation. Care should also be taken to avoid giving modern meaning to the medieval use of certain stock words and terms.)

Significant later source are;

• Thompson, M.W., 1998, Medieval bishops' houses in England and Wales (Aldershot: Ashgate Publishing) p167
  Coulson, C., 1982, 'Hierarchism in Conventual Crenellation' Medieval Archaeology Vol26 p93
  Turner, T.H. and Parker, J.H., 1859, Some account of Domestic Architecture in England (Oxford) Vol3 pt2 p403

More details about licences to crenellate can be found here.

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