[1] MacDermott was born in County Louth, but became a successful merchant in Dublin and obtained property in Montserrat.
He implemented Jacobite policies in Dublin, including stringent wartime price controls on goods within the city.
On 3 July 1690, MacDermott fled Dublin following the Jacobite defeat at the Battle of the Boyne.
In April 1692 he petitioned for a pardon in order to return to Ireland, stating his willingness to be loyal to the government of William III of England; this was rejected.
In September 1695, James II instructed him to surrender the mayoral chain to Sir William Ellis.