Born 28 July 1859 at Fahan, Londonderry, Ireland, the seventh child of the five sons and three daughters of John Gibson Thomson of Ardrishaig, Argyllshire, civil engineer, a pupil of Thomas Telford, and his wife Catherine, a daughter of John Sinclair of Lochaline House, Morven, Sound of Mull. Mrs J G Thomson was born on 5 January 1818 and died in 1909 (*Oban Times*, 27 March 1909). He was educated at the village school at Ardrishaig till he was ten, when he went to King's School, Peterborough, and was afterwards apprenticed to his eldest brother, William, who was in practice at Peterborough. He passed the first London MB from private study during this time. William Sinclair-Thomson, MD Glasgow 1869, FRCS Edinburgh 1879, had been a pupil of Lister in Scotland but, as Lister moved to London, St Clair was sent to King's College Hospital, entering as a student on the same day, 1 October 1877, that Lister entered as professor of surgery. Here he won prizes and scholarships and served as house surgeon to Lister in 1883. William Sinclair-Thomson later moved from Peterborough to the West End of London, where he long carried on a successful general practice. St Clair Thomson next became resident medical officer at Queen Charlotte's, and made some voyages to the Cape of Good Hope as surgeon in a Union Castle liner. While at Queen Charlotte's he adopted the strictest Listerian methods, and no mother or infant was lost during his term of office. He next had the chance of travelling in Europe as personal physician to a rich invalid, who was an enthusiastic amateur of works of art. Thomson acquired a mastery of several languages, and developed his taste and artistic knowledge by frequenting the great galleries of the continent. He practised for seven years among the British colony at Florence in the winters and at St Moritz in the Engadine in the summers, for which purpose he took the MD of Lausanne by examination in 1891. Feeling that he had no scope for his ambition he then attended the clinics and lectures of the laryngologists of Vienna: Leopold Schroetter, Ritter von Kristelli, Carl Stoerk, and in particular Markus Hajek, and also Adan Politzer, the professor of otology. After further study at Freiburg, Frankfort, and Paris he came back to London in 1893, took the Fellowship at the end of the year, and set up as a consultant laryngologist. He often recalled the happy summer days at the Redehof in Vienna. To fill the lean years he sub-edited *The Practitioner* and later edited *The Laryngoscope*, lectured at the London Policlinic, and made important researches on nasal bacteriology at the Lister Institute. These he published in collaboration with Richard Tanner Hewlett (1865-1940). He also worked with W D Halliburton, FRS (1860-1931) on the cerebrospinal fluid. His election as surgeon to the Royal Ear Hospital and physician to the Throat Hospital in Golden Square provided him with clinical experience. In 1901 he was appointed assistant physician to the throat department at King's College Hospital, but he developed tuberculosis of the lung and larynx and had to go to a sanatorium under the care of Patrick Watson-Williams (1863-1938). Here he rigorously endured the regime of silence, perhaps the first patient in England to do so; for six months he was dumb. He had hardly recovered from this check when his wife died (1905); they had been married in 1899. Thomson turned with energy to his clinic at King's College Hospital and also worked at the Seamen's Hospital. His appointment as throat physician to King Edward VII helped greatly to increase his private practice. In 1903 he was elected FRCP, ten years after his admission as FRCS, and in 1911 he permanently established his fame by his book *Diseases of the Nose and Throat*, which became the bible of his specialty, and ran to four editions in his lifetime. Thomson was particularly interested in tuberculosis of the larynx, from which he had himself suffered, and his appointment as laryngologist to the King Edward VII Sanatorium at Midhurst gave him opportunities for valuable clinical work and observation. In 1924 the Medical Research Council published his account of ten years' experience there. At King's College Hospital he became ultimately consulting physician and emeritus professor of laryngology, and he was elected a Fellow of King's College. He was unanimously invited to take the chair at the students' celebration of the centenary of King's in 1930. He was also consulting laryngologist to the Italian Hospital, Queen Square, and to the Throat and Eye Hospital, Maidstone, and professor of laryngology and otology at the Royal Army Medical College. Thomson was consulting throat physician to the Actors' Association and to the Association of Music Hall Artistes, and physician to the Royal Italian Opera. He had counted among his friends Beerbohm Tree, George Alexander, and Charles Wyndham, and was a frequenter of the Old Vic and Sadler's Wells and the Malvern and Stratford dramatic festivals. Deafness in later years made him transfer his interest from plays to ballet. He kept up his continental connexions throughout his life, and received many professional and public honours abroad. He was promoted in 1916 from being a foreign correspondent to foreign associateship in the Académie de Médecine at Paris, and he was a member of the American Laryngological Society. He was officier of the Légion d'Honneur and also received the Médaille de Réconnaissance française. In Belgium he attended King (then Prince) Leopold III in 1915 and was created commendateur of the Ordre de Léopold, and he was a commendatore della Corona d'Italia. He frequented Fontainebleau and Vittel and loved to ride there, and in London he rode regularly in the Row, maintaining that riding and dancing were the best exercise. Thomson usually travelled in a large yellow Rolls-Royce car, which with its distinguished-looking occupant attracted much attention. Till an advanced age he often spent the week-ends sculling on the river at Long Wittenham. He took an active part in professional societies, becoming president of the Medical Society of London in 1915-16, when he gave a learned presidential address on Lettsom and the founders of the Society. From 1925 to 1927 he was president of the Royal Society of Medicine; and while holding this office enabled the Society to obtain the grant of an achievement of arms, and presented a chain and badge for his successors. To mark his presidency one hundred and seventy-five laryngologists presented him with a loving-cup in 1926. He had already been president of the sections of otology and of the history of medicine within the Society. He was president of the National Association for the Prevention of Tuberculosis, which he had helped to found. He was three times president of the section of otolaryngology at annual meetings of the British Medical Association: in 1909 at Belfast, in 1930 at Winnipeg, when he received the honorary Doctorate of Laws from the University of Manitoba, and at the centenary meeting in London in 1932. In 1913 he was president of the section of laryngology at the last International Medical Congress. He was knighted in 1912. At the Royal College of Physicians he served as an examiner 1924-26, and on the Council 1925-27; he was awarded the Weber-Parkes medal and prize for his researches in tuberculosis in 1936, and in 1924 had delivered the Mitchell lecture on "Tuberculosis of the larynx, and its significance to the physician". He gave the Semon lecture before the University of London; he was founding president of the University of London Medical Graduates Association from 1927, the inaugural meeting having been held in his house. Thomson practised at 64 Wimpole Street, where he also collected the fine furniture and works of art among which he delighted to dispense princely hospitality. His elder sister, Matilda (Maud) Louisa Thomson, kept house for him; she outlived him, dying on 30 January 1944, aged 90. He was a skilled and charming speaker and a fluent writer. Though somewhat pompous and affectedly formal with strangers, he was beloved by his friends and a loyal, humane, and amusing companion with a cultivated knowledge of the world and its good things. Though the air of worldly self-assurance did not fail to provoke jealousy, he was an accomplished peace-maker, possessing great tact and suavity. Thomson had a cat-like love of comfort and told against himself how, after a train accident near Lyons, he had refused assistance at Professor Léon Eugène Bérard's clinic, only to find himself, when the clinic was already full, more injured than he had thought and compelled to endure the rigours of the Salle des Blessés at the Hotel-Dieu. In his last years he consciously paraded his valetudinarianism, and his death from the results of a street-accident was cruelly ironic. Thomson died at Edinburgh on 29 January 1943, at the age of 83. A memorial service was held at Golder's Green crematorium on 3 February. Thomson had been living in Scotland since 1940, when his London house was damaged in an air-raid. He left £1,000 each to the Royal Medical Benevolent Fund and to the Royal Society of Medicine, and £500 each to the Royal Colleges of Physicians and Surgeons and to Epsom College, and on the death of his sisters £4,000 to the Royal Society of Medicine and £500 each to the Royal College of Physicians and Epsom College, as well as other charitable bequests. Thomson delighted to honour his famous teachers, particularly Hajek and Lister. He gave to the Royal College of Surgeons his own notes of Hajek's lectures of 1893, and welcomed Hajek himself when he came to England as a refugee from German tyranny in 1938. Of Lister he wrote an account: "Joseph Lister, personal memories" in the *King's College Hospital Gazette* for October 1927, and deposited one thousand reprints at the Hospital, so that each new student for many years might receive a copy. He gave the Royal College of Surgeons three autographs of Lister in 1941. In 1883 he had exhibited with his master at the Medical Society of London the first six cases of wiring the patella, and recalled the occasion at a meeting in the same room fifty-six years later. Thomson stated that he had never seen the vocal cords or the ear-drum in the living when he qualified, and that the only operation for adenoids then known was for the surgeon to scratch them out blindly with his nail while the hospital porter held down the child-patient. His first book was a translation from the German of A Onodi's *Anatomy of the nasal cavity*, published in 1895. In 1910 he reported the first British case of the successful removal of a foreign body, a shawl-pin, impacted in the secondary bronchus. His most original contribution to surgery was the operation of laryngo-fissure for intrinsic cancer of the larynx, a subject second only to tuberculosis in his interests, and one on which he wrote a book in collaboration with Lionel Colledge, FRCS. He was attracted to the study of cancer of the larynx through the work of Sir Henry Butlin and Sir Felix Semon, FRCP; and he improved the technique of their operation of thyrotomy for limited cancers of the vocal cord. Publications: A Onodi. *The anatomy of the nasal cavity*, translated 1895. Microorganisms of the healthy nose, with R T Hewlett. *Med-chir Trans*, 1895, 78,239-266. The fate of microorganisms in inspired air, with R T Hewlett. *Lancet*, 1896, 1, 86. *The cerbro-spinal fluid, its spontaneous escape from the nose; with observations on its composition and function in the human subject*. London 1899; New York 1901. *Diseases of the nose and throat, comprising affections of the trachea and oesophagus*. London, 1911; 2nd edition, 1916; 3rd, 1926; 4th, with V E Negus, 1937. Shakespeare and medicine, annual oration. *Trans Med Soc Lond* 1915-16, 39, 257-325. John Coakley Lettsom and the foundation of the Medical Society of London, presidential address, October 1917. *Trans Med Soc Lond* 1917-18, 41, 1-61, with map and 2 plates. Tuberculosis of the larynx; ten years' experience in a sanatorium. *Medical Research Council, Special Report Series*, 83, 1924. Antimonyall cups, pocula emetica or calices vomitorii. *Proc Roy Soc Med* 1925-26, 19, history p 123-128, with coloured plate. Joseph Lister, personal memories. *King's Coll Hosp Gaz*, Oct. 1927; also as a special illustrated reprint, with cover-title Lister 1827-1912, *a house-surgeon's memories*, 1938. *Cancer of the larynx*, with Lionel Colledge. London, 1930.