'Mac' Crooks was born on 21 January 1909, the son of David Mackenzie Crooks. He was educated at Epworth College and studied medicine at Liverpool University, where he qualified in 1931. He held junior posts at the Northern Hospital, Liverpool, and at the Shropshire Orthopaedic Hospital, Oswestry. He then became senior house officer at Selly Oak Hospital, Birmingham, and All Saints Hospital, London. In 1935 he was commissioned into the Medical Branch of the RAF, passed the FRCS in 1937, and went to Palestine in 1938 where he worked as a general surgeon, dealing with the many casualties of the Arab revolt. He was in the operating theatre all round the clock, and was mentioned in despatches. In the New Year of 1941 he was posted to the RAF General Hospital Habbaniya, Iraq, as a surgeon. In May 1941 the base was besieged by rebels under the pro-Nazi Raschid Ali who had seized power in Baghdad, intending to provide Hitler with a Middle East base. There were several days of heavy artillery bombardment until the relatively inexperienced young pilots, flying Airspeed Oxford Trainers and Fairey Gordon biplanes, drove off the far better equipped Iraqi Air Force. After the war he returned to pass the MCh of Liverpool University in 1945 and was seconded as a clinical tutor for a year to Edinburgh University, before returning to Egypt where he served from 1950 to 1951 and was awarded the OBE. In 1952 he was appointed consultant in orthopaedic surgery to the RAF and in 1955 became the senior consultant surgeon to the RAF. He virtually rebuilt the orthopaedic branch of the RAF medical services which had been so prominent during the war and whose legendary figures such as Watson Jones and Osmond Clarke had all left. He travelled extensively, teaching, consulting and operating. He was appointed CBE in 1963 and honorary consulting surgeon to the Queen in 1966 and remained adviser in orthopaedics to the RAF. He retired in 1970 to Cornwall, where he continued to do locum work for some years, and found time to enjoy his hobbies of gardening and golf. He married Mildred Gwyther in 1936; they had two sons, David and Richard, and a daughter, Elizabeth. He died on 12 March 1992, aged 83.