Alexander returned to Britain in May 1920 as a major, second in command of the 1st Battalion, Irish Guards; in May 1922, he was promoted substantive lieutenant-colonel and appointed commanding officer. He commanded the battalion at Constantinople (a sensitive posting in the runup to the Chanak Crisis), then Gibraltar from October 1922, then in London from April 1923 until January 1926, when he was released from that role to attend Staff College, Camberley. Alexander was then in February 1928 promoted to colonel (backdated to 14 May 1926) and was the next month appointed Officer Commanding the Irish Guards Regimental District and 140th (4th London) Infantry Brigade, part of 47th (1/2nd London) Division, in the Territorial Army, a post he held until January 1930, when he again returned to study, attending the Imperial Defence College for one year. There, two of Alexander's instructors—the future field marshals Alan Brooke and Bernard Montgomery—were unimpressed by him.