The Gatehouse website record of a licence to crenellate for Bretby Castle granted on 1301 March 19

Original source is;

Lyte, H.C. Maxwell (ed), 1895, Calendar of Patent Rolls (1292-1301) p. 580 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;

Turner, T.H. and Parker, J.H., 1859, Some account of Domestic Architecture in England (Oxford) Vol. 3 part 2 p. 404 online copy

Seagrave (Segrave), John, second Lord Seagrave (1256–1325)

Seagrave (Segrave), John, second Lord Seagrave (1256–1325), soldier and baron. Seagrave actively served in Edward's wars in Wales and Scotland and was made the King's lieutenant in Scotland in 1302.

At the end of C12 the Earl of Chester granted Caludon to Stephen de Segrave (d. 1241). He is believed to have been responsible for erecting the first house at the site.
In 1300 he was given twelve oaks for timber from Cannock Forest, and ten oaks from Whittlewood Forest, for the construction of a chapel at Chalcombe Manor. In 1301 he paid £800 for custody of the lands of his wife's father, Hugh de Plessis, together with the marriage of Hugh's heirs. In the same year he was given licence to crenellate his dwelling at Bretby in Derbyshire and, four years later, his manor at Calvedon. In 1305 Seagrave was also given permission to hold fairs and markets at Woodweston in Huntingdonshire, which was extended to his manor at Fenstanton in the same county in 1315, and to Aspel in Warwickshire in 1318. In September 1312 he was given the choice of lands to the value of £100 yearly (for him and his heirs) or the grant of £1000 to buy such lands. (Musson)

Biographical source include;

A. J. Musson, 2004, ‘Seagrave , John, second Lord Seagrave (1256–1325)’ Oxford Dictionary of National Biography (Oxford University Press) online copy (subscription may be needed)

More information about licences to crenellate can be found here.

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