Primarly copies of Cockcroft's articles, 1925-1967, lectures and speeches, 1936-1967, correspondence, 1920-1967, and material relating to his association with various educational establishments, particularly Churchill College, of which he was the first Master, but there are also his Cavendish Laboratory notebooks from 1927-1946, papers of the Kapitza Club (an informal gathering of Cambridge physicists organized by the Russian physicist, Peter Kapitza) from 1922-1966, papers and articles he collected on Lord Rutherford, certain papers relating to atomic energy, and material on scientific training and policy as well as interesting personal correspondence with fellow scientists and his famous "black book" research diaries from 1938-1967.