"Licence for William Plompton, knight, and his heirs to construct walls and towers around and within his manor of Plompton, co. York, and to crenellate the same, and to enclose and impark all his lands, meadows, feedings, pastures, woods and other tenements in Plompton, and grant to them of free warren and free chase in the above, so that no one shall enter therein to hunt without licence under forteiture of 10l., although the above are within the metes of the king's forest or chace of Knaresburgh, co. York."
Granted at Westminster, by privy seal.
William Plompton was granted a licence to crenellate in 1474, along with licence to impark all his lands in Plompton
Original source is
(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;
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