John Ainsworth was inspector of manuscripts with the Irish Manuscript Commission. John was the son of Edina Hope, fourth daughter of the 4th Marquess Conyngham of Slane. Sir John spent much of his youth at Slane. Educated at Eton and Cambridge John became inspector of manuscripts in 1943 and later held the same position in the National Library of Ireland. John attended the funeral of his grandfather in Slane in 1939. He wrote many reports on collections of manuscripts in private ownership, many of which were published in Analecta Hibernica. He succeeded to his father’s title in 1971 and died in 1981 and was buried at Slane.