The Gatehouse website record of a licence to crenellate for Markenfield Hall granted on 1310 Feb 28

Licence to John de Merkyngfeld, king's clerk, to crenellate his dwelling house at Merkyngfeld, co. York. By p.s. (CPR)

Johannes de Merkyngfeld ... mansum suum ... Merkyngfeld, Ebor. (Turner and Parker)

Rex omnibus et fidelibus suis ad quos &c. salutem. Sciatis quod concessimus et licentiam dedimus pro nobis et haeredibus nostris dilecto et fideli nostro Johannis de merkyngfeld quod ipse
mansum suum de merkyngfeld in comitatu Ebor muro de petra et calce firmare et kernellare et mansum illud sic firmatum et kernellatum tenere possit sibi et
haerebibus suis imperpetuum sine occasione vel impedimento nostri vel haeredum nostrorum justitiariorum ... aliorum ballivorum seu ministrorum nostrorum quorumcumque In cujus &c.
teste rex apud Westm xxviii die ffebr per breve de privato sigello (transcription by Philip Davis for image of Patent Roll C66/133 mem 18 reproduced in Curteis)
The king to all bailiffs and his liegemen, to whom, &c,, greeting— Know that we have granted and given licence on behalf of ourselves and our heirs to our beloved and taithful John of Markenfield, that he may strengthen and crenellate with a wall of stone and lime his manor of Markenfield, in the County of York and that he may hold it, so strengthened and krenellated, for himself and his heirs for ever, without penalty or impediment from us, or our heirs, justiciaries {...} or others our bailiffs or officers whosoever. In witness whereof &c. Witness the king at Westminster, on the 28th day of February. By writ of the Privy Seal. (translation by Philip Davis)

Original source is;

Lyte, H.C. Maxwell (ed), 1894, Calendar of Patent Rolls (1307-13) p. 212 online copy
Curteis, Ian, n.d. c. 2010, Markenfield Hall (Windsor: Wilton) p. 7
TNA C66/133 mem 18

(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. Licentia is best translated as 'freedom to' not 'permission'.)

Significant later sources are;

Emery, Anthony, 1996, Greater Medieval Houses Vol. 1 (Cambridge) p. 421
King, D.J.C., 1983, Castellarium Anglicanum (London: Kraus) Vol. 2 p. 541n140a
Turner, T.H. and Parker, J.H., 1859, Some account of Domestic Architecture in England (Oxford) Vol. 3 part 2 p. 406 online copy

John de Markenfield