In 1336, John de Molyns was possibly granted, by Edward III, a Royal licence to crenellate (Aston Mullins)

There is insufficient evidence to be certain about this possible licence to crenellate.

I can't find this in the rolls.

Significant later source are;

• Emery, Anthony, 2006, Greater Medieval Houses Vol3 (Cambridge) p211

Moleyns , Sir John (d. 1360)

John de Molyns, although described as the king's yeoman, was Treasurer to Edward III and was eventually knighted. His later career was an almost textbook 'robber baron'.
Moleyns [Molyns, Molines], Sir John (d. 1360), administrator and criminal, was the son of Vincent Moleyns and his wife, Isabella; he came from Hampshire, where his father had stood surety for a knight of the shire returned to parliament in 1301. His recorded career began in the royal household, as an adherent of the Despensers. In the autumn of 1325 he accompanied Prince Edward to France, and delivered a letter to the bishop of Winchester there. He married Egidia Mauduit, daughter of Sir John Mauduit and granddaughter of Robert Poges, who claimed a share of the manor of Stoke Poges, Buckinghamshire. Egidia and her husband profited from the murder of Peter Poges, lord of the manor, and his heir in the autumn of 1326, and Moleyns was later indicted of this crime but acquitted, though by a jury partly selected by himself. Stoke Poges became the centre of his estates which extended over thirty-one manors and tenements at the time of their confiscation in December 1340. (Röhrkasten)

Biographical source include;

• Jens Röhrkasten, ‘Moleyns , Sir John (d. 1360)’, Oxford Dictionary of National Biography, Oxford University Press, 2004 [http://www.oxforddnb.com/view/article/18909, accessed 28 Nov 2007]

More details about licences to crenellate can be found here.

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