Background
Maurice was born the eldest son of David McKay Cassidy, a doctor at the Lancaster Mental Hospital in Lancashire and was educated at Lancaster Grammar School and Clare College, Cambridge.
Maurice was born the eldest son of David McKay Cassidy, a doctor at the Lancaster Mental Hospital in Lancashire and was educated at Lancaster Grammar School and Clare College, Cambridge.
He then entered Street Thomas" Hospital in London as a medical student, qualifying Bachelor of Medicine in 1906 and Doctor of Medicine in 1909. After working there for several years, including two as Resident Assistant Registrar, he was elected in 1913 a Fellow of the Royal College of Surgeons and joined the honorary staff of Street Thomas". In 1914 he delivered the Goulstonian Lecture to the College of Surgeons on the subject of rheumatoid arthritis.
During the First World War he spent two years in a Calais hospital, where he contracted pulmonary tuberculosis and had to be repatriated.
In addition to his commitments at Street Thomas" he was for some time Chief Medical Officer to the Metropolitan Police and was knighted C.B. on his retirement from the post in 1929. Although he had withdrawn from active duty at Street Thomas" prior to the Second World War he nevertheless returned to duty for the duration of the war, retiring finally in 1945.
He delivered the Harveian Oration to the Royal College of Physicians in 1946 on the subject of coronary disease. From 1946 to 1948 he served as President of the Royal Society of Medicine.
In 1930 he had been appointed Physician to the Royal Household, and later Physician in ordinary to both King George V and King George VI. He was created first Knight Commander of the Royal Vicrorian Order and then Knight Grand Cross of Royal Victorian Order
He died at his home in London in 1949 following a car accident.