He then returned to Chatham and went to Cambridge University. In 1925, he returned to India and was placed on special duty at Kabul in the foreign and political department. In 1926 he returned to Nowshera as garrison engineer and spent several years in Works Services at Peshawar where he made full use of this engineering genius designing bridges. Also in 1925, he married Ruth Carolyne, daughter of G. E. Wakefield. They had three sons, two of whom went on to serve in the Royal Engineers. On 1 June 1929, Jefferis was promoted to captain.