In 1337 Aug 12, Johannes de Coloygne (John Cologne) was granted, by Edward III, (In year 11 of his reign) a Royal licence to crenellate Cornhill (Cornhill, London)

"dilectus vallettus noster ... domos suas super Cornhill infra civitatem nostram"

Granted at Tower of London, by privy seal.

Original source is

• Calendar of Patent Rolls (1334-38) p505

(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 source are;

• Emery, Anthony, 2006, Greater Medieval Houses Vol3 (Cambridge) p439
  Coulson, C., 1995, 'Battlements and the Bourgeoisie: Municipal Status and the Apparatus of Urban Defence' in Church, Stephen (ed), Medieval Knighthood Vol. 5 (Boydell) p194n297
  Turner, T.H. and Parker, J.H., 1859, Some account of Domestic Architecture in England (Oxford) Vol3 pt2 p411

John de Coloygne (d. 1363)

John de Coloygne seems to have been a merchant who dealt, at least in part, in pearls since a dispute over his will, in 1363, was about an outstanding debt for 11,500 pearls. This amount of wealth suggest the licence had some practical consideration. He is described as 'kings yeoman' which normally would imply royal service but I've not been able to trace a position and the only other record is one of him receiving payment for providing gowns to knights serving in the Scottish wars of the 1330's.

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