[1] He was the eldest son of Simon Brook and his wife Ida (née Jansen), both Lithuanian Jewish immigrants from Latvia.
He served with the Royal Army Medical Corps from 1944 to 1947, in the later stages of Second World War and immediately afterwards, in the Far East: in India, Burma and Indochina (now Vietnam).
His experiences in the war, of the effects of poor morale, led him to pursue a career in mental health.
He specialised in psychoanalytic psychotherapy at the Cassel Hospital in Richmond from 1956, and moved to the Tavistock Clinic in 1971.
He retired from the NHS in 1985 but continued to practise as an honorary consultant psychotherapist at St Mark's Hospital in Harrow from 1986 to 1995.