In 1338 June 8, Galfridus le Scrop (Geoffrey Le Scope) was granted, by Edward III, (In year 12 of his reign) a Royal licence to crenellate Burton Conestable (Constable Burton Hall)

"quoddam fortalicium apud manerium suum de Burton Constable de novo construere et forticium illud muro de petra et calce firmare et kernellare.
Licence for Geoffrey le Scrope to impark his woods of Burton Conestable, Coverham and Caldebergh, if they be not within the metes of the forest, and to build a crenellated fortalice at his manor of Burton Conestable."

Granted at Lopham, by privy seal.

Licensed to build a 'crenellated fortalice' and to impark his woods

Original source is

• Calendar of Patent Rolls (1338-40) p94

(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
  Turner, T.H. and Parker, J.H., 1859, Some account of Domestic Architecture in England (Oxford) Vol3 pt2 p412

More details about licences to crenellate can be found here.

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