In 1141 July, Com Gaufredo Essexiae (Geoffrey de Mandeville) was supposedly granted, by Matilda, a Royal licence to crenellate unum castellum ubicunque voluerit in terra sua (anywhere in his fief)

"Conceda etiam eidam Gaufredo quod novum castellum quod firmavit super Lviam stet et remaneat ad efforciandum ad voluntatem suam. Concedo etiam ei quod firmet unum castellum ubicunque voluerit in terra sua, sicut et per aliam cartam meam concessi, et quod stet et remaneat."

Granted at Oxford,

Although this document has been considered by some as a licence to crenellate the current opinion rejects this as a licence to crenellate.

A charter between Empress Matilda and Geoffrey de Mandeville, part of his 'king making' activities during the Anarchy, an similar grant (Round, p142) by King Stephen may predate Matilda's. Not, in a meaningful sense, a licence to crenellate although has been called this by some.

Original source is

• Great Coucher (But in missing volumes)
  Lansdowne MS. 229 (fol. 109)
  Regesta Regum Anglo-Normannorum Vol3 p99-103

(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., 1994, 'Freedom to Crenellate by Licence - An Historiographical Revision' Nottingham Medieval Studies Vol38 p104n50
  King, D.J.C., 1983, Castellarium Anglicanum (London: Kraus) Vol1 p273n2
  Coulson, C., 1982, 'Hierarchism in Conventual Crenellation' Medieval Archaeology Vol26 p95n2
  Round, J.H., 1892, Geoffrey de Mandeville (Oxford) p168, 174-5 [dated 1142]

Mandeville, Geoffrey de, first earl of Essex (d. 1144)

Biographical source include;

• C. Warren Hollister, ‘Mandeville, Geoffrey de, first earl of Essex (d. 1144)’, Oxford Dictionary of National Biography, Oxford University Press, 2004 [http://www.oxforddnb.com/view/article/17927, accessed 15 Feb 2008]
  

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