In 1345 Aug 5, Prior et Conventus Roff. was granted, by Edward III, (In year 19 of his reign) a Royal licence to crenellate Rochester (St Andrews Priory, Rochester)

"licence for the prior and convent of Rochester to build a wall of stone and mortar from the east gate of the city of Rochester as far as the gate of St. William, between the city and their orchard, and crenellate the same.
quendam murum de petra et calce a porta orientali civitis Roff usque ad Portam Sancti Guilli. inter dictam civitatem et gardinum eorundem Prioris et Conventus facere, &c. et kernellare"

Granted at Westminster, by privy seal.

Original source is

• Calendar of Patent Rolls (1343-45) p539

(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;

• Coulson, C., 1982, 'Hierarchism in Conventual Crenellation' Medieval Archaeology Vol26 p94
  Page, Wm (ed), 1926, 'Houses of Benedictine monks: The cathedral priory of St Andrew, Rochester' VCH Kent Vol2 p121-26
  Turner, T.H. and Parker, J.H., 1859, Some account of Domestic Architecture in England (Oxford) Vol3 pt2 p414

More details about licences to crenellate can be found here.

Please let me know if you see any errors, can add information or can otherwise help to improve this resource. Contact me