Born Rewi Rawhiti Macintosh, he was the younger son of Charles Nicholson, newspaper editor and at one time mayor of Timaru, and Lydia Beatrice (née Thompson) Macintosh. Timaru-born Sir Robert Reynolds Macintosh was eduacted at Waitaki Boys' High School before serving as a pilot in the Royal Flying Corps in the First World War. He later qualified from Guy's Hospital, London, and became a a partner in a private anaesthetic practice in London. He later practiced in the Spanish Civil War on the Nationalist side, though his motivation was primarily humanitarian. In the Second World War he served as an adviser to both the Royal Air Force and the Royal Navy, running training courses and furthering research in a number of areas. He also sdeveloped the laryngoscope blade during the war. Source: Plarr's Lives of the Fellows Online.

Served as an adviser in anaesthetics to both the Royal Air Force and the Royal Navy during WWII. AWMM