His mother, Violet Oakeshott, a Quaker and pacifist, was instrumental in sending him to Leighton Park School, Reading, from where he won an exhibition to St John's College, Cambridge, to study natural sciences, in which he gained a third class degree.
In 1931 he was appointed medical officer at the Maudsley Hospital, London, where he was encouraged by his chiefs Aubrey Lewis and Edward Mapother to apply statistical methods to the empirical study of mental illness.
By this time Nazi persecution of Jewish professionals was well under way, and on Mapother's initiative the Rockefeller Foundation started providing funds enabling the Maudsley to receive prominent psychiatrists expelled from their posts in Germany.
The director of the Munich Institute and head of its genetics department was Ernst Rudin, the predominant architect and rationaliser of Hitler's eugenic sterilization policies and implicated in Action T4.
As he wrote, "It was a source of peculiar satisfaction to me to be showing what I thought of Nazi Rassenhygiene by marrying a Jewess, a member of an inferior race by their standards, a lady of the highest genetical aristocracy by mine."
[2] Slater would later refer to the Nazis as 'unspeakable men' and 'devils' with a 'detestable ideology', and noted the Nazification of the Munich institute when he left in 1935, claiming to have never seen much of Rudin and to only recall once interacting socially with him at a ceremonial dinner at his home.
[4] With the outbreak of war in 1939 the Maudsley was evacuated, and Slater became clinical director of the Sutton Emergency Hospital, where he had responsibility for the treatment of some 20,000 psychiatric casualties.
[1] In an article published in a eugenics journal in 1947, Slater tentatively suggested that group differences between Jews and Christians might disappear (along, therefore, with antisemitism) due to inter-breeding.
[citation needed] Meanwhile, he continued his own research as senior lecturer at the Institute of Psychiatry, notably on the prevalence of psychiatric disorders in twins (with James Shields).
[9] It has been noted that originally (1944) they wrote that their judgements of efficacy – in the absence of any known theoretical basis for it – were on purely empirical (research) grounds, but later (e.g. 1963) they justified them as the insights of the careful and attentive observer.
[11] Slater died at his home in Barnes, London, on 15 May 1983, being survived by his first and second wives and by the four children of his first marriage – a mathematician, a haematologist, a psychiatrist and an English don.
He found the psychological difficulties raised by the orthodox view of William Shakespeare of Stratford-upon-Avon's authorship "most insuperable" but resolutely stuck to a principle of open-mindedness without pitching for any other candidate.