During the preparation of the editions of the first Duke's correspondence and at other stages during his life, various other collections of papers were acquired and became embedded with his own papers and copies were also taken of correspondence in other hands.
Further collections of papers were presented to later Dukes of Wellington. Notable groups include papers of Sir John Cox Hippisley, first Baronet, relating to plans for attacking the Spanish colonies in Latin America, c.1804-8 (WP1/185-6), and to Catholic emancipation, 1794-1819 (WP1/1069/1-16); papers of the second Earl of Liverpool (Harcourt papers); papers of Lieutenant Colonel J.Gurwood, the editor of the Dispatches; correspondence of William Fitzgerald, second Baron Fitzgerald and Vesey; some items from the papers of George IV; records of the Adjutant General's department for the Peninsular War (WP9/1), together with military secretary's papers and papers of Lord Fitzroy Somerset for the same period (WP9/2); copy letter books of Henry Bathurst, third Earl Bathurst, for letters to the Duke of Wellington, 1813-16 (WP10); papers of Richard Colley Wellesley, first Marquis Wellesley, principally 1798-1802 (WP11); correspondence of Henry Wellesley, first Baron Cowley, with the first Duke of Wellington, 1810-15, and Henry Wellesley's letter book as ambassador at Vienna, containing his correspondence with George Canning, 1823-6 (WP12); and the diary of Henry Richard Charles Wellesley, first Earl Cowley, as ambassador to France, 1852 (WP13). Copies were taken of papers of the first Earl of Eldon after his death in 1838 and during the 1870s copies were made of the correspondence of Prince Metternich in Vienna. A series of maps from India, the Peninsular War and later forms WP15.
Another group of papers, separated from this archive in the 1860s and containing the papers of Christopher Collins, the Duke's manservant, is now University of Southampton Library MS 69.