Walter Russell Brain, son of Walter John Brain, a Reading solicitor, was educated at Mill Hill and New College, Oxford. It was probably under the guidance of Sherrington that he began an interest in neuro-physiology, and was influenced to devote his medical career to clinical neurology.

His undergraduate clinical training was at the London Hospital. He became physician to the Maida Vale Hospital for Nervous Diseases in 1925, and to the London Hospital in 1927. He gained an international reputation in neurology, was editor of the main textbook of neurology of his time, and for many years was editor of 'Brain' and the 'Quarterly Journal of Medicine'.

He was elected to the office of president of the Royal College of Physicians in 1950, and was probably the youngest physician to hold that position. He served on many government committees in Britain during his years in office, but in spite of his administrative responsibilities, he was able to continue his loyal service to his hospitals as a clinical neurologist, and to maintain his contributions to English literature.

He was a man of imposing appearance, never ruffled, never angry, and a man of whom Lord Moran wrote, 'he could claim descent from a long line of presidents of the RCP who have had one foot firmly planted in the world of books... He spoke as he wrote, with clarity and conciseness. He was completely without vanity and when he had said he had to say, he sat down...'.

In 1955, while president of the London College, he was made a Fellow of The Royal Australasian College of Physicians, 'honoris causa', together with the Prime Minister of Australia, Sir Robert Menzies, and the Governor General of Australia, Sir William Slim. These remarkable men of renown in diverse fields of service and learning must have made an imposing presence which may never be equalled in the College.

Lord Brain married Stella Down, and they had two sons and one daughter. The elder son Christopher succeeded to the family honours, and the youngest son Michael followed his father into medicine, becoming professor of haematology at McMaster University in Canada.