Research papers of Cecil Vaughan Owen, relating mainly to the history of Montgomeryshire and including: Llanidloes and Llangurig School minute books, 1904-1972; leaflets, press cuttings, posters, sale catalogues and other source materials, and notes on the history of Llanidloes and Montgomeryshire and various local churches, 1800-1980; notes for lectures and talks, 1969-1979; an unpublished typescript 'Arwystli through the ages', [mid-late 20th century]; card index of timber-framed buildings in Montgomeryshire; offprints of articles on the archaeology and history of Montgomeryshire; reviews, correspondence and notes relating to his publications, 1949-1975; guides to castles and ecclesiastical buildings, [1970s]; correspondence, leaflets, press cuttings and other material relating to Cambrian Archaeological Association, Society of Antiquaries, Powysland Club and other bodies, 1948-1980; personal papers, including correspondence; records relating to Llanidloes parish church, 1906-1980; and records relating to the Glanyrafon estate, Montgomeryshire, 1866-1899.

Records and correspondence, 1566-1766, relating primarily to the administration of the Herbert of Cherbury estates in Montgomeryshire and Shropshire (together with some in Worcestershire, Merionethshire and Monmouthshire), but also including some Dolguog material, as well as Cherbury records and correspondence relating to current affairs, household and personal business, personal news, and the maintenance of individual members of the family. Also included are a few records concerning the family’s official responsibilities in Montgomery.

Records, 1587-1754, relating to the government of Montgomery, Shropshire, Wales and the marches, as well as the administration of the Cherbury and Powis Castle estates.

Ledger and journal of Gaewern Slate works, Machynlleth, 1835-1856; accounts and notebooks of the Ratgoed and Cymerau Slate Quarries, Tal-y-llyn, and Llwyngwern Slate Quarry, Llanuwchllyn, 1853-1899; ledgers and notebook of the Cambrian Slate Works, Machynlleth, 1899-1909; minute books of the Abercorris Slate Quarry Company, Rhiwgwreiddyn, Corris, 1893-1909, and the Towyn Company, Tywyn, 1893-1903; and miscellaneous accounts and ledgers, 1827-1909.

Papers of Stuart Rendel and family members, including papers relating to the University College of Wales, Aberystwyth, and the proposal to establish the National Library of Wales and its development during the early years of its existence, 1883-1916; speeches, addresses and political papers relating to disestablishment of the church in Wales and the 1889 Intermediate Education Act, 1882-1909; press cuttings, 1881-1913; photographs, 1892; miscellaneous letters, 1878-1912; letters to Stuart Rendel, 1853-1912, including letters from A. C. Humphreys Owen, 1877-1905, family letters, 1853-1902, and letters from prominent political figures and Welsh public figures; letters and copies of letters from Rendel, 1880-1912; diaries, mainly recording details of Stuart Rendel's business activities, 1863-1869; notes of conversations with W. E. Gladstone, John Morley and H. H. Asquith, 1888-1910; papers relating to Chinese affairs and French and Chinese peace talks, 1884-1886; papers of James Meadows Rendel, including letters, 1828-1856, and papers relating to his estate, 1856-1859; letters of Catherine Jane Rendel, 1845-1855; letters and papers of George Wightwick Rendel, 1871-1902; papers relating to Rendel's other brothers, 1841-1889, and his daughters, 1882-1910; letters and papers of Harry Stuart Goodhart-Rendel, 1898-1959, and other papers concerning him, 1963-1977; papers, mainly letters, of the Goodhart family, 1819-1957; papers of Miss Rosemary Rendel, 1986-1996; papers of Sir George William Rendel, including: Foreign Office papers, 1917-1967, correspondence, 1912-1973, papers relating to the Catholic Union of Great Britain, 1942-1979, lectures, diaries and notes, 1915-1954, personal and family papers, 1908-1980, and material relating to the book The Sword and the Olive (1957), 1954-1986.

Papers, 1889-1963, of Prof. Roderick Urwick Sayce, including notes by him on anthropology, archaeology, geology and geography, together with drafts and offprints of publications written and collected by him, his personal papers and correspondence, and a considerable amount of material collected by Professor A. C. Haddon, Professor of Zoology at the Royal College of Sciences and Assistant Naturalist to the Science and Art Museum of Dublin, relating to Irish folklore, including correspondence between Sayce and Haddon.