In the mid-1930s he was awarded a Rockefeller travelling fellowship to Harvard University where he worked with Stanley Cobb and collaborated with Fred Gibbs in his pioneering work on the application of EEG to the study of cerebral disease. It was at this time that he developed his lasting interest in epilepsy.[1]
In 1936 Denis Williams returned and brought the first electroencephalograph machine that was used regularly for clinical work in the UK.[1] He qualified MRCP in 1937 and graduated MSc in 1938. During WWII he became a squadron leader in the Royal Air Force Volunteer Reserve and worked at the Military Hospital for Head Injuries[3] under Charles Symonds, who was knighted in 1946. Williams graduated DSc in 1942 and was elected FRCP in 1943.[1] Symonds and Williams published in 1943 Clinical and Statistical Study of Neurosis Precipitated by Flying Duties.[4] Williams was promoted to wing commander before demobilisation.
He had married Joyce, daughter of Frank Beverley Jewson, in 1936. She was herself a qualified medical practitioner and a Justice of the Peace. They had four children; two sons and two daughters. One son predeceased him.[1]
^Symonds CP, Williams DJ (1943). Clinical and Statistical Study of Neurosis Precipitated by Flying Duties – Flying Personnel Research Committee Report 547. London: Medical Research Council. (republished as Chapter X in Air Publication 3139 (1947). London: Her Majesty's Stationery Office)