"libere et quiete tenendum omnibus liberis consuetudinibus cum quibus aliquis comes Anglie tenet castella sua"
Although this document has been considered by some as a licence to crenellate the current opinion rejects this as a licence to crenellate.
Supposedly a retrospective licence, although Round writes this a royal confirmation of William's possession of the castle. Not, in a meaningful sense, a licence to crenellate although has been called this by some.
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;
Roumare, William de, first earl of Lincoln (c.1096–1155x61), justice...During 1137 he attested for King Stephen in Normandy, and was among those appointed as justiciars there. Probably in 1139 Stephen appears to have made him earl of Cambridge, a title he had relinquished by 1142 when he was earl of Lincoln. The most plausible date for his creation as earl of Lincoln is shortly before Christmas 1140, when Stephen visited Lincoln and increased his honours and those of Ranulf, earl of Chester. Stephen's visit may have been intended to deal with Ranulf, who is said to have seized Lincoln Castle in 1140 after the king had helped Henry, the son of King David of Scotland, Ranulf's rival for Carlisle, to avoid a trap which Ranulf had set for him. It is possible that Stephen's grant of increased honours was part of a peace agreement, and included some form of rights in Lincoln Castle. Alternatively, it is possible that Stephen had come in peace to Lincoln and bestowed the comital title, but no rights in the castle, on Roumare, and that Ranulf's seizure of the fortress followed the king's departure. Whatever the case, the half-brothers were besieged by the king when he returned to Lincoln during the Christmas festival of 1140. With the help of Ranulf's father-in-law, Robert, earl of Gloucester, they defeated and captured Stephen at the battle of Lincoln on 2 February 1141. (Dalton)
Biographical source include;
More details about licences to crenellate can be found here.
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