Born 28 November 1874, the second son of Sir Thomas Smith, Bart, consulting surgeon to St Bartholomew's Hospital, and his wife Ann Eliza, second daughter of Frederick Parbury. Thomas Smith had been appointed surgeon to St Bartholomew's the year before Gilbert's birth. His elder son, Sir Rudolph Hampden Smith, second baronet, also became a Fellow of the College. Gilbert Smith was educated at St Bartholomew's, where he served as house surgeon to W J Walsham, and as clinical assistant in the throat department. He was also clinical assistant in the children's department at the Middlesex Hospital. At the Durham MD examination, 1900, he won the gold medal for his thesis on actinomycosis. In 1900 Smith settled at Hindhead, near Haslemere, Surrey, in partnership with Dr Arnold Lyndon. The practice grew large and successful, and Smith ultimately became the senior of six partners. In the first world war he went to France with the British Red Cross, was commissioned in the RAMC in 1917, and served as surgical specialist at a base hospital at Rouen. He married on 1 August 1900 Elizabeth Adeline, third daughter of William Carson, of Bryn Estyn, Chester, who survived him with four sons and two daughters. He died on 22 June 1950 at The Chalet, Hindhead, near Haslemere, aged 75, and was buried at St Luke's, Grayshott. Smith was one of the first country practitioners to drive a car, which he did from 1902. He was captain of the Hindhead Golf Club, and enjoyed fishing and shooting in Scotland and Yorkshire.