Born at Tiverton, Devon in 1849, son of Frederick Mackenzie, MRCS 1838, coroner to the borough of Tiverton. He was educated at Blundell's School, then still housed in the town of Tiverton but now outside it, and came to the London Hospital for his medical training. He served the Hospital as resident accoucheur, junior resident medical officer, house surgeon, medical assistant, and resident medical officer, and then returned to practice in his native town, where he remained for the rest of his long life. He took a prominent part in the professional and public life of his town and county, becoming an alderman of Tiverton and chairman of the public health committee of the Devon County Council and of the medical subcommittee of the Devon education committee. During the war of 1914-18 he acted as tuberculosis officer for Devonshire. He was also coroner for the borough of Tiverton, as his father had been, and medical officer to Blundell's School, and a Justice of the Peace for both borough and county. He was elected a freeman of Tiverton. He was for many years surgeon to the Railway Passengers Assurance Society, and in 1907 was vice-president of the section of diseases of children at the Exeter meeting of the British Medical Association. Mackenzie died at Avenel, Tiverton, on 30 October 1942, aged 93, being then the senior Fellow of the College, and was buried at Chevithorne.