47 volumes, covering 1880-1920, accumulated while Hardinge held Foreign Office posts. The bulk of the material consists of original holograph letters from Hardinge's friends and colleagues in ambassadorial and other posts abroad. There are also some typescript copies of Hardinge's letters and original correspondence with Lord Curzon of Kedleston. For the period at St Petersburg, 1904-1906, there are two volumes of Foreign Office confidential prints (the official dispatches from Hardinge to Lord Lansdowne, Secretary of State for Foreign Affairs), a diary and a letter-book. The papers also contain copies of memoranda, reports, newspaper cuttings and a variety of personal material relating to Hardinge.
Material accumulated while Hardinge was Viceroy of India, containing correspondence with persons in India, with persons outside India, with the Secretary of State for India, and with King George V, Lord Stamfordham and others; printed telegraphic correspondence with the Secretary of State for India; printed correspondence relating to the European War; memorandum on questions likely to arise in India at the end of the war; and speeches by Lord Hardinge. These papers include around 30 volumes of original personal and semi-official letters, as well as other manuscript material, and approximately 50 printed volumes, produced on the Viceroy's private press for his own use.
The collection also contains papers transferred from Kent County Archives. This material is in three main sections: Official papers, containing diplomatic papers for 1856-1916; Viceregal papers, 1907-1916, containing administrative papers, general correspondence, personal papers, special reports on the Persian Gulf and presentation albums; Miscellanea, 1914-1941, covering links with India, personal papers and retirement papers.