After the war, Crocker left the army to train as a solicitor. However, he did not enjoy his new profession and returned to soldiering as an infantry officer in the Middlesex Regiment (Duke of Cambridge's Own) in the Regular Army. His rank of lieutenant was confirmed on 16 December 1920 (with seniority backdated to 20 December 1919), the same year of his marriage to Hilda Mitchell; they had a daughter, Roberta (b. 1921) and a son, Wilfrid (b. 1923). From 13 January 1922 Crocker was seconded to the Royal Tank Corps (later the Royal Tank Regiment) to specialise in the then new field of armoured warfare. His secondment became a permanent transfer in August 1923 (backdated to June 1919).