He developed an addiction to gambling and squandered away a large part of his inheritance, running up substantial gaming debts and by 1750 was threatened with arrest.
[1] In November 1761, an attempt by MacNaghten and his followers to abduct Mary Ann from a carriage on a family journey to Dublin Parliament and elope with her failed, when he shot and mortally wounded her by mistake.
Tradition portrays John MacNaghten as the heroic rogue of Irish folklore who rebelled against the authority of the landowning class and, in challenging them, was seen to have fought against them.
His immense loyalty to his servants and followers, especially his manservant Thomas Dunlap who was hanged immediately after MacNaghten, has presented him in the myth as a champion of the under-class.
As for the attempted kidnap of Mary Ann, the practice of abduction and marriage was prevalent in 18th century Ireland among young men of social standing but with little property.