||Probably the leading naval architect of his day, Tennyson D'Eyncourt was trained at Armstrong's yard at Elswick and at the Royal Naval College, Greenwich. On completion of his apprenticeship, he remained with Armstrong's until 1898 when he became naval architect to Fairfields on the Clyde. In 1902 he returned to Armstrong's and made a reputation both for technical competence as well as skill in securing foreign orders. In 1912, D'Eyncourt was appointed Director of Naval Construction and thereby became responsible for the British wartime shipbuilding programme, as well as for the development of tanks and airships. He retired in 1924 and rejoined Armstrong's until they amalgamated with Vickers in 1927. Afterwards he acted as a consulting naval architect and was connected with numerous institutions such as the National Physical Laboratory, the Worshipful Company of Shipwrights and the Royal Institution of Naval Architects He published an autobiography, 'A shipbuilder's yarn; the record of a naval constructor' (London, 1948).
||The papers were presented by the widow of Sir Eustace's son, Lady Pamela Tennyson D'Eyncourt, in 1972. The majority are loose papers, 1898 to 1939. Many are copies of official memoranda on particular ships, the development of the tank and on general topics, while there are subject files of correspondence for the post-1924 period.