 A manuscript purporting to be the "Notebook of Sir John Northcote, containing Memoranda of Proceedings during the first session of the Long Parliament, 1640" was published in 1887.However, its authenticity was challenged on the grounds that it covered a period before Sir John had a seat in the House.Northcote married Grace Halswell (died 1675), a daughter and heiress of Hugh Halswell (d.1626) of Chamberlain Street, Wells, Somerset, by his wife and cousin Elizabeth Brounkard.