Born at Pilgrims Rest in the Transvaal on 14 January 1876, the sixth and youngest child of Thomas McLachlan, a pioneer from Perth, Scotland, and Maria Shires, his wife, who came from Cheshire, England. He received his early education at Maritzburg College and at Brighton Grammar School. He qualified from Guy's Hospital where he served on the resident staff for eighteen months. He then returned to Cape Town and acted as a civil surgeon with the forces in South Africa. In 1902 he was appointed assistant medical officer at the New Somerset Hospital. Later he settled at Salt River and Observatory as a general practitioner. He was railway medical officer at Salt River and harbour medical officer, having in addition the busiest practice in the peninsula during 1904-14. During the war of 1914-18 he was attached to the South African Medical Corps, and saw service in Egypt and France. The war ended, he returned home and devoted himself wholly to surgery. He was appointed additional surgeon to New Somerset Hospital, surgeon to Woodstock Hospital and later to Rondebosch Hospital, He soon won for himself a reputation as one of the leading surgeons in Cape Town, both for his skill and the great care he devoted to his patients. He was much interested in the affairs of the British Medical Association, and was president of the South Africa division in 1932. McLachlan married in September 1911 Margaret Constance, daughter of the Rev Mr Baxendale. She survived him with three children, two sons and a daughter. He died at Caterham, Valley Road, Claremont, Cape on 21 October 1939. He is described as a man of great heart, with wide charity, in whom unassuming modesty was combined with a firm will. "A stranger walking into one of his wards and seeing him stooping over the bed of a patient would inevitably behold the idealised picture of surgeon. Tall and distinguished, with clean-cut features and white-haired he was the model of the stage surgeon."