In 1387 Dec 29, Henricus, episcopus Norwicen (Bishop Henry Despencer) was granted, by Richard II, (In year 11 of his reign) a Royal licence to crenellate North Elmam (North Elmham Bishops Castle)

"Licence for the king's kinsman, Henry, bishop of Norwich, to crenellate his manors (manerium) of North Elmam and Gaywode, co. Norfolk."

Granted at Westminster, by privy seal.

Original source is

• Calendar of Patent Rolls (1385-89) p381

(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;

• Cushion, B. and Davison, A., 2003, Earthworks of Norfolk (Dereham: East Anglian Archaeology 104) p119-20
  Liddiard, R., 2000, Landscapes of Lordship (Oxford: BAR 309) p108
  Thompson, M.W., 1998, Medieval bishops' houses in England and Wales (Aldershot: Ashgate Publishing) p168
  King, D.J.C., 1983, Castellarium Anglicanum (London: Kraus) Vol2 p312n12
  Turner, T.H. and Parker, J.H., 1859, Some account of Domestic Architecture in England (Oxford) Vol3 pt2 p283, 420

More details about licences to crenellate can be found here.

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