Papers relating to his military career, 1939-1962, principally his service in Burma, 1939-1941, UK, 1941-1943, North Africa, 1943, Italy, 1943-1944, and Korea, 1955-1956, notably including battalion orders for 2 Bn, Sherwood Foresters, 1945; German propaganda leaflets for US and Allied troops, [1944]. 'An ancient Yorkshire family', a history of the Slingsby family, written by Slingsby in 1989.

Papers relating to his service in the Far East in 1942-1945 and 1950, dated 1942-1945 and 1950, principally comprising two photograph albums of Keijo (Seoul) POW camp, 1942-1944; copy of obituary from The Lancashire Lad, North Lancashire Regt (Loyal Regt) journal (Dec 1950); copy of covering letter to the Centre from Joan Procter (Procter's sister), 1992.