John received his medical education at Bartholomew's Hospital- entering as a student in 1908. He graduated B.SC. in 1911; obtained the diplomas of M.R.C.S., L.R.C.P. in 1914; and then graduated M.B., B.S. the same year. He took up a temporary commission in the R.A.M.C. and was attached to the Royal Air Force. John was the son of Wyndham and Emma Randall of Bridgend, Glamorgan.