Hill, Arthur Blundell Sandys Trumbull (1788–1845), 3rd marquess of Downshire , KP, and major Irish landowner, was born 8 October 1788, eldest of the five sons of Arthur Hill (qv), 2nd marquess, and his wife Mary Hill (qv), only surviving child of Lord Sandys; there were also two daughters. By the time he died, Downshire's property in Ireland totalled more than 110,000 acres, most of which lay in Co. Down but including also substantial estates in the south around Blessington, Co. Wicklow, and Edenderry, King's Co. (Offaly). He succeeded his father in 1801 when still a minor, his mother (who became Baroness Sandys in her own right in 1802) acting as guardian till he came of age in 1809. He was educated at Eton and Oxford. He married (25 October 1811) Maria, eldest daughter of the 5th earl of Plymouth, by whom he had two sons and two daughters.
Finding the property heavily encumbered not only with family charges but also with the very large personal debts of his father and grandfather, Downshire made it his aim to pay off the personal debts in full as a matter of honour. Despite setbacks, he succeeded so well that he was able in addition to invest nearly £150,000 in buying more land. The system he instigated in 1813, which involved a complete reorganisation of management structure and office procedures, was carried into effect by an able new chief agent at Hillsborough, William Reilly. A large-scale map survey of the whole property, townland by townland, completed during the minority, became the basis for changes in leasing and rents. Rents were raised wherever possible as agricultural prices rose during the war years, but the scope for doing so was limited by the large number of existing long leases – many of which had been granted recently by the marchioness. Peace with France was to bring a postwar slump, when arrears accumulated and rents had to be reduced. Some property was sold and, for a man of his status and pretensions, Downshire chose to live in comparatively modest style, above all eschewing the prodigal expenditure on politics that his father, mother, and grandfather had indulged in.
The Downshire papers in PRONI, a major historical archive, reflect the quite extraordinary personal input of the 3rd marquess in the management of his estates throughout the whole period between his coming of age and his death. In particular, a vast collection of correspondence – some 30,000 letters in all – demonstrates the extent to which this untypical Irish landlord intervened directly. Many of the letters, to employees and tenants at all levels, are in his hand. Many more were written in response to his instructions and expostulations. They show a man of principle who, though doing all in his power to maximise his income, had a genuine interest in agricultural improvement, encouraging tenants to adopt better practices, sponsoring farming societies, subsidising drainage schemes, and so on. He also had a keen interest in education, both nationally and locally, taking an active part in the work of the Kildare Place Society and establishing many schools on his estates (he made sure, though, that such good works were well publicised in the newspapers). He patronised many worthy bodies such as the linen board and the RDS, as might be expected. Less predictably, he was interested in the Irish language and was president of the Ulster Gaelic Society (founded 1830).
In politics Downshire was by instinct deeply conservative, but also pragmatic, following the lead of Wellington (qv) and Robert Peel (qv) in voting for catholic emancipation despite his abhorrence of Daniel O'Connell (qv). A devout pillar of the established church (though, despite being a tithe-owner, critical of the tithe system), he was one of the chief movers of a mass meeting of protestants at Hillsborough in 1834 at which the presbyterian minister Henry Cooke (qv) proclaimed ‘the banns of marriage’ between presbyterians and episcopalians in defence of civil and religious liberty.
High-minded, if also at times high-handed in manner and self-important, Downshire worked hard himself and expected all his employees and tenants to be equally conscientious. Naturally he was often disappointed. He was particularly concerned about his failure, despite all efforts and exhortations, to make his southern estates as efficient and well behaved as those in the north. Though an absentee owner in the south, he visited both Blessington and Edenderry regularly. It was on one of these periodic tours of inspection that he dropped dead at Blessington on 12 April 1845. He was buried at Hillsborough. The funeral attracted an enormous crowd of mourners and was reported at some length in the Illustrated London News. His memory is perpetuated in an impressive pillar monument, with his statue on top, erected at Hillsborough in 1848.