1792 he was unanimously elected rector. To this post was attached the rectory of Twyford in Buckinghamshire, with a right of residence at the rectory of Combe (Lipscomb, Buckinghamshire, iii. 132–3). He expended part of his income on improvements to the rectorial houses at Twyford and Combe, about ten miles from Oxford, and he is described as ‘a munificent contributor to the improvements at the college,’ presumably to the front quadrangle, which he defaced with incongruous battlements.
Tatham preached about 1802 a famous sermon, two hours and a half long, in defence of the disputed verse in St. John's first epistle (v. 7). Its directness of speech was as remarkable as its learning (Brown, Life of J. A. Symonds, i. 141). Tatham concluded the discourse by leaving the subject to the learned bench of bishops, ‘who have little to do and do not always do that little.’
Tatham, who was usually at open war with his fellow members of the hebdomadal council, vehemently opposed the views advocated by Cyril Jackson and the new examinations which had been instituted through his influence at the university. He issued in 1807 an ‘Address to the Members of Convocation on the proposed New Statute for Public Examinations,’ and it was followed by several pamphlets of a similar kind, including ‘Address to Lord Grenville on Abuses in the University’ (1811), and ‘Oxonia Purgata: a Series of Addresses on the New Discipline’ (1813).
In the closing years of his life he chiefly lived at Combe rectory. He scarcely ever appeared at Oxford, unless it was to bring with him in his dogcart a pair of pigs of his own breeding to be exposed for sale in the pig-market. The college did not prosper in his hands. Many caricatures and lampoons of him passed from hand to hand at Oxford, and he was known as ‘the devil’ who looked over Lincoln.
On the nomination of the trustees of the Bridgewater estate, Tatham when a very old man, was appointed in 1829 to the rectory of Whitchurch in Shropshire. He died at the rectory-house in the parish of Combe on 24 April 1834, and was buried in the church of All Saints, Oxford, where a monument was erected by the widow to his memory. He married, in 1801, Elizabeth, the wealthy daughter of John Cook of Cheltenham. She died on 24 Aug. 1847, having founded at Lincoln College, in her husband's memory, a scholarship of the annual value of fifty guineas, limited in the first instance to candidates born or educated in Berkshire (cf. Gent. Mag. 1851, i. 443–4). Tatham's personal appearance was attractive, with a ‘fine countenance and a bright eye,’ and he was gifted with a vigorous expression of speech, the effect of which was heightened by a broad Yorkshire dialect. A portrait of him, for which he is said to have paid 300l., is at Lincoln College.
Tatham's chief work was his set of Bampton lectures, entitled ‘The Chart and Scale of Truth by which to find the Cause of Error,’ vol. i. 1790, vol. ii. n.d. [1792] (Nichols, Lit. Anecd. iii. 703). A new edition, ‘revised, corrected, and enlarged’ from the author's manuscripts at Lincoln College, and with a memoir, preface, and notes, by E. W. Grinfield, came out in 1840. This extraordinary series of discourses, famous in its day ‘for ponderous learning and its vigorous, if coarse, style,’ embodied a new system of logic. His principle was that truth ‘becomes varied and modified as it passes through the human faculties,’ and that it pervades the various departments of general knowledge, being finally summed up in ‘the summum genus of knowledge, the knowledge of revealed theology.’ Edmund Burke called on Tatham soon after its publication, and expressed high approbation. Dr. Thomas Reid and David Doig admired it, and the article on ‘Logic’ in the fourth edition of the ‘Encyclopædia Britannica’ was almost wholly taken from it. Tatham admired and imitated the style of Warburton.
Besides several separate sermons, characteristically polemical, which he preached at Oxford, Tatham published: 1. ‘Oxonia Explicata et Ornata’ (anon.), 1773; 2nd edit. improved and enlarged (anon.), 1777. He anticipated the erection of a martyr's memorial, and advocated architectural improvements at Oxford (cf. Lascelles, Oxford, 1821, pp. 90–8, 258–91). It would appear that he published about 1815 a further tract on ‘Architectural Improvements in Oxford.’ 2. ‘Essay on Journal Poetry,’ 1778; a confused work (cf. Monthly Review, lviii. 398–9). 3. ‘Twelve Discourses introductory to the Study of Divinity,’ 1780. 4. ‘Letters to Burke on Politics,’ 1791; the first was on ‘the principles of government,’ the second on ‘civil liberty.’ They contained some severe reflections on Dr. Priestley. On 1 July 1791 there appeared in the daily prints a letter from Tatham to the revolution society, declining an invitation to dinner (Gent. Mag. 1791, ii. 671, 1123). 5. ‘Letter to Pitt on the National Debt,’ 1795. 6. ‘Letter to Pitt on a National Bank,’ 1797. 7. ‘Letter to Pitt on the State of the Nation and the Prosecution of the War,’ 1797. 8. ‘Plan of Income-tax,’ 1802. He claimed to have invented the
