In 1315 Aug 28, Thomas, comes Lancastr (Thomas, second Earl of Lancaster) was granted, by Edward II, (In year 9 of his reign) a Royal licence to crenellate Dunstanburgh (Dunstanburgh Castle)

"Licence to the king's kinsman, Thomas, earl of Lancaster, to crenellate his dwelling-place of Dunstanburgh (mansum suum de Dunstanburgh), co. Northumberland."

Granted at Lincoln,

The stone for Dunstanburgh was begun to be quarried on May 7, 1313 and much of the castle was built in that and the following year, so the licence was a post factum one, or at most legalised the finishing touches to the battlements.

Original source is

• Calendar of Patent Rolls (1313-17) p344

(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) p159
  Bates, C.J., 1891, Border Holds of Northumberland (London and Newcastle: Andrew Reid) p9
  Turner, T.H. and Parker, J.H., 1859, Some account of Domestic Architecture in England (Oxford) Vol3 pt2 p407

More details about licences to crenellate can be found here.

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