Sheehan, John (1809–82), journalist, was born in Celbridge, Co. Kildare, the only son of Thomas Sheehan, a prosperous farmer, and Alicia Sheehan (née Dunn). John was educated at Clongowes Wood College, where he was tutored by Francis Sylvester Mahony (qv), better known as ‘Fr Prout’, and entered TCD in October 1827 but never graduated. In 1830 he joined the Comet Club, a literary and political club conspicuous for the youth and talent of its members. These included the writer, musician, and painter Samuel Lover (qv), the dramatist Joseph Stirling Coyne (qv), the future editor of the Morning Post, Robert Knox (qv), and Maurice O'Connell (qv), son of Daniel (qv). The club's first action was the preparation of a pamphlet, The parson's horn book, published in two parts (1830). A satirical and boisterous undergraduate attack on the tithe system and the established church, it enjoyed huge and immediate success and, due to the brilliance of Lover's etchings, subsequently became a collector's item. Encouraged by this venture, the club produced from 1 May 1831 a weekly magazine entitled The Comet, which ran to 104 issues. Sheehan was appointed sub-editor, with the older and more experienced Thomas Browne as editor. The paper quickly achieved a substantial circulation and had the distinction of being the first to publish James Clarence Mangan (qv). However, in autumn 1832 an article by Browne, entitled ‘Black slugs’ and dealing with the established church, encouraged an action for libel. Browne and Sheehan were arrested, and though they enjoyed the best defence counsel in the country, O'Connell and Robert Holmes (qv) respectively, they were sentenced in January 1833 to a fine of £100 each and a year's imprisonment. The fine was never exacted nor the full sentence served. Browne was sent to Newgate, Dublin, and Sheehan to Kilmainham; within a few months the former was released in exchange for voluntary exile to America, and the latter with no such stipulation. However, the Comet had been suppressed and Sheehan was so chastened by his experiences that he left for England and made no further attacks on government or church for the remainder of his life.
In London he continued with journalism, working as a parliamentary reporter for the Morning Herald, and in 1836–7 as correspondent in Madrid and Paris for the short-lived Constitutional newspaper, on which he was a colleague of Thackeray. He is said to have been the original of ‘Captain Shandon’ in Thackeray's Pendennis, but this claim is also made for the brilliant, self-destructive Cork writer, William Maginn (qv), who is the more likely model. Sheehan returned to Dublin in January 1843 to enter the King's Inns and was subsequently admitted to the English bar and may have practised for a short period. He was briefly (1852) proprietor and editor of the Independent of London and Cambridge, and appears to have lost money through this. His pecuniary struggles were ended by marriage (16 December 1848) to a wealthy widow, Ellen Shubrick, whose late husband, Maj. Henry Shubrick, was an Anglo-Indian officer. This permitted Sheehan to travel around Europe and to write self-indulgent articles for such magazines as Temple Bar, the Gentleman's Magazine, and the Dublin University Magazine, frequently under the pseudonyms ‘Knight of Inishowen’ and ‘The Irish Whiskey Drinker’. His main interest in these publications was the retelling of his youthful radicalism and imprisonment. He died at Charterhouse on 29 May 1882.