The collection primarily concerns Denison's political career and contains correspondence with the leading social and political figures of the day, including William Gladstone. The correspondence touches on most political issues of the day, including successive reform bills, the Irish potato famine, the Crimean War, European political affairs, educational reform and matters of parliamentary procedure. The collection also contains personal diaries from the 1820s as well as detailed diaries of official affairs from 1857. These diaries formed the basis for the posthumous publication, 'Notes from my Journal when Speaker of the House of Commons' (London, 1899).
Denison had deep religious beliefs and, given his political stance, a natural concern with matters relating to Church and State. This interest is reflected in his instigation of a work of biblical criticism known as 'The Speaker's Commentary on the Bible'. The collection includes much correspondence on the subject from editors, publishers and leading clerics.
The collection also reflects Denison's wider non-parliamentary interests, as a member of the landed aristocracy. He was a progressive landlord, interested in agricultural improvements, and he became president of the Royal Agricultural Society. His correspondence with the Duke of Portland, Lord Lonsdale and others touches on issues of drainage, irrigation and the steam plough. He was also an observant traveller; the collection includes notebooks from his 1826 and 1853 European tours.
Papers of a family nature include deeds, such as the marriage settlement of Denison and Lady Charlotte Cavendish-Bentinck. In addition, there are items of ephemera, including among Lady Charlotte's papers a number of puzzles and acrostics.