The papers cover the period, 1879-1916, and include papers on Howell's service as a correspondent for The Times in the Balkans, including photographs and newspaper cuttings, 1903; papers on Howell's training at Staff College, Quetta, India, and Staff College, Camberley, Surrey, including notes on Cavalry organization and tactics and on the establishment of Frontier Intelligence organization in India, 1904-1914; papers on service as Officer Commanding 4 Hussars, including Operational orders, accounts of Allied operations on Western Front, personal diaries and manuscript maps of Western Front trenches, 1914-1915; Operational orders from service as Brig Gen, General Staff Cavalry Corps, Western Front, 1915; official and semi-official correspondence from service as Chief of Staff, Salonika, including personal diaries, correspondence relating to attempts to secure Bulgarian entry in World War One on the Allied side, and correspondence relating to allegations of Howell leaking memoranda to a Suffragete newspaper called Britannia, 1915-1916. The collection also includes Howell family correspondence, 1879-1889, mostly between Howell's father and grandfather, and from 1909-16 between Howell and his wife Mrs Rosalind 'Linnett' Howell [nee Buxton].

The papers of Howell's wife, Mrs Rosalind 'Linnett' Howell [nee Buxton], 1910-1966, include an account of Howell's life entitled, Philip Howell. A Memoir By His Wife (1942, London, George Allen & Unwin Ltd) and letters from Capt (Edward) Hugh Buxton and Maj (Abbot) Redmond Buxton [Rosalind 'Linnett' Howell's brothers], concerning Allied withdrawal from Anzac Cove and Sulva Bay, Gallipoli, Turkey, 1915-1916.