The Gatehouse website record of a licence to crenellate for Servats Tower, London granted on 1305 Oct 3

Licence for William Servat, citizen and merchant of London, to build of stone and lime and crenellate a turret beyond the gate of his dwelling-place in that city. By p.s. (CPR)

Willielmus Servat, civis et mercator, London ... quandam turellam ultra portam mansi sui in Civitate praedicta, petra et calce de novo construere et Kernellare ... Lond., Midd. (Turner and Parker)

Granted at Sheen. Grant by privy seal.

Comments

It has been argued that this tower was built to defend Servat's stock (Williams, 1975) but Coulson is dismissive of this idea as maligning of city peace keeping. Certainly status consideration must have been foremost in obtaining such a licence (and building such an expensive tower), but surely security can not be entirely dismissed as a contributing factor. Coulson writes "The privy seal warrent was for Servat 'to kernel and fortify as strongly (i.e. here as ostentatiously) as he pleases a torelle which he has made over the porte of his house in London'. The Great Seal clerks toned it down to standard form, it seems".

Original source is;

Lyte, H.C. Maxwell (ed), 1898, Calendar of Patent Rolls (1301-7) p. 379 online copy

(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;

Davis, Philip, 2010-11, 'Crenellated town houses in Medieval England' Castle Studies Group Journal Vol. 24 p. 270-91
Emery, Anthony, 2006, Greater Medieval Houses Vol. 3 (Cambridge) p. 439
Coulson, C., 1995, 'Battlements and the Bourgeoisie: Municipal Status and the Apparatus of Urban Defence' in Church, Stephen (ed), Medieval Knighthood Vol. 5 (Boydell) p. 194n297
Coulson, C., 1994, 'Freedom to Crenellate by Licence - An Historiographical Revision' Nottingham Medieval Studies Vol. 38 p. 119-20
Harben, H.A., 1918, 'Sernes Tower', A Dictionary of London
Turner, T.H. and Parker, J.H., 1859, Some account of Domestic Architecture in England (Oxford) Vol. 3 part 2 p. 405 online copy

Servat, William (d. 1318/19)

Wm. Servat was an alderman of Walbrook Ward 1309 and 1318. He sat in Parliament in 1309 and 1313 and was a Collector of Customs (Beavan, I. 216, 163, 380) for the King. Servat was already lending to the king by 1283, and helped finance the defence of Gascony after the fall of the Riccardi in 1294. By 1302 he had a lucrative contract to supply the royal wardrobe with spices, linen, cloth, and furs, and in that year, with partners from Montpellier and Provence, met almost a quarter of the wardrobe's demand for spices... In or shortly before 1302 he moved from Cordwainer ward to take over the former headquarters of the Riccardi in Bucklersbury, the heart of London's financial district. In 1305 he obtained licence to crenellate the house and to build a stone tower above its gateway, a notable symbol of success. Alderman for Walbrook from 1308 until his death, he represented the city in parliament in 1309 and 1313. The scale of Servat's dealings with the crown, however, did not match that of the leading Italians with whom he sometimes did business. Eventually he was eclipsed by Edward II's ambitious Genoese banker, Antonio Pessagno, who early in 1313 was rumoured to have purchased his tower; the deal was in fact completed by 1315. In the summer of that year, which perhaps marked Servat's effective retirement from business, the king's outstanding debts to him amounted to £2246. Almost half that sum had been contracted under Edward I, and in December 1318 a third of it was still due. (Keene)

Biographical source include;

Derek Keene, 2004, ‘Servat, William (d. 1318/19)’ Oxford Dictionary of National Biography (Oxford University Press) online copy (subscription may be needed)