Peter was born in Pretoria, South Africa. He migrated to Sydney in 1975 to take up his new responsibilities as professor and head of psychiatry at Sydney University — and to raise his family in Australia. Peter was an imposing figure, being both tall and large. He spoke about his physique and girth with self-effacing humour. His imposing presence was softened by his relaxed posture and a broad, open and welcoming smile.

Peter's parents, Joseph Beumont and Gladys Natalie (nee Baynes), were respectively of Belgian and English ancestry. Joseph was a successful clothing manufacturer. Peter was the youngest of their six children by seven years. Both parents were linguists, a gift they bestowed on Peter. At Pretoria University he initially enrolled in arts but switched to medicine. He met his future wife, Daphne Theron, when both were undergraduates. Daphne completed her occupational therapy degree and pursued that career when family commitments allowed. They married in 1961. Daughters Tasha and twins Rochelle and Claire were born in 1968 and 1970 - by which time the Beumonts had moved to the United Kingdom. All three daughters graduated in economics at Sydney University, have married and have successful but diverse careers.

Peter was educated at the Christian Brothers School in Pretoria. He completed his undergraduate training in 1962, with the first place in psychiatry at Pretoria University. In 1963, he was a junior house officer in Glasgow. Between 1965 and 1968 he was a senior house officer and then a registrar at the Maudsley Hospital. In 1969, he held a senior registrar appointment at the Maudsley and Bethlem Hospitals. Between 1969 and 1971 he held an appointment at Oxford. The Beumonts' then returned to South Africa where between 1971 and 1972, Peter was a senior specialist at the Groote Schuur Hospital. He was promoted to acting head of that hospital and of the university department between August 1973 and July 1974.

In November 1975 Peter took up his responsibilities as professor and head of the Department of Psychiatry at the University of Sydney. The chair had been vacant since the departure of Professor David Maddison in 1974. Peter revised the undergraduate curriculum and established his clinical and research base at the Royal Prince Alfred Hospital. The undergraduate program prospered throughout Peter's tenure. In 1975, the academic staff numbered one full professor (himself), one associate professor and two lecturers sited at four hospitals: The Royal Prince Alfred Hospital, Concord Hospital, Rozelle Hospital and the Royal North Shore Hospital. Peter effected a policy of decentralization of the university departmental activities. By 1998, when the department's centenary year was celebrated, its academic staff had grown to include twelve professors, six associate professors, two university-funded senior lecturers and many junior clinical academics. The department then spanned campuses as far afield as Richmond, the Nepean and Canberra. By then Peter had persuaded outstanding academic psychiatrists to join the University of Sydney and to lead its clinical institutions. Peter encouraged a broad spectrum of postgraduate studies within the department. In later years Peter established links between the department and those at the University of Trier and at Santiago de Compostela. He left a personal legacy of postgraduate clinicians specializing in eating disorders. Peter continued as head of psychiatry until 1999, following which he maintained a personal chair and continued to work until a severe respiratory illness took his life in October 2003.

During 1975, his first year at the Royal Prince Alfred Hospital, Peter established the first specialist unit for patients with eating disorders in New South Wales. For more than a quarter of a century he vigorously campaigned for better recognition and treatment of patients with eating disorders. He was equally tireless in his advocacy for better clinical facilities and improved consultation and referral processes throughout New South Wales.

His good friend, Professor Gerald Russell, described Peter's output of original research publications as 'prodigious'. Indeed, he co-authored over 400 papers and book chapters and co-edited 11 books. Peter's initial interest in dieting disorders, evident at the Maudsley Metaboloic Unit, remained a lifelong passion. His MSc thesis was on the neuroendocrinology of eating disorders. Russell attributes to Peter many seminal ideas about eating disorders and acknowledges Peter's significant contribution to their classification and management. In recognition of his achievements Peter was awarded the Gaskell Gold Medal and Prize of the Royal College of Psychiatrists in 1971, the Max Plank Research Award (with Prof. Karl Pirke) in 1994 and Membership of the Order of Australia in 2001.

Peter's intellectual interests were many, including philosophy, especially the philosophy of religious thought, Egyptology, etymology and languages. His political sympathies and values can be guessed from the fact that he had, for a time, been physician to Mrs Helen Suzman, the sole Member of Parliament for the anti-apartheid Progressive Party. Peter's outdoor pleasures included proximity to the ocean, swimming and fishing. However, his main passion was his family.