In 1348 Nov 18, Matilda, quae fuit uxor Johannis de Marmyon, militis (Matilda [Maud] widow of Sir John Marmion) was granted, by Edward III, (In year 22 of his reign) a Royal licence to crenellate Westcanfeld [Westtanfeld] (Tanfield Castle)

"Licence for Maud late the wife of John de Marmyoun, knight, to crenellate the manor (manerium) of Westtanfeld, co. York."

Granted at Westminster, by privy seal.

Licence to crenellate granted to Sir John Marmion in 1314, for his house called L'Ermitage' and repeated in 1348 when granted to his widow Matilda Depending on the date of the abandonment of the site at Magdelan Field this may refer to either site (or it's possible the 1348 licence was for the new house)

Original source is

• Calendar of Patent Rolls (1348-50) p210

(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;

• Emery, Anthony, 1996, Greater Medieval Houses Vol1 (Cambridge) p421
  King, D.J.C., 1983, Castellarium Anglicanum (London: Kraus) Vol2 p541n141a
  Turner, T.H. and Parker, J.H., 1859, Some account of Domestic Architecture in England (Oxford) Vol3 pt2 p415

More details about licences to crenellate can be found here.

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