 He accompanied The 4th Earl of Chesterfield to Dublin as his chaplain, upon the Earl's appointment as Lord Lieutenant of Ireland.Twysden was nominated to the Bishopric of Raphoe in Ulster on 3 March 1746 and was consecrated by the Lord Archbishop of Dublin, assisted by the bishops of Derry and Clonfert, at St Michan's Church, Dublin, on 29 March 1747.Bishop Twysden died on 2 November 1752 at home in Jermyn Street, St James's, London.