Born in 1799, his mother being the daughter of Dr Madan, Bishop of Peterborough, and the 'Miss Madan' of the poet Cowper's correspondence. This lady died when her son was young, and his education was undertaken by an aunt. After apprenticeship he became a student at St Bartholomew's Hospital in 1819. He first practised at Clapham, and was unsuccessful, but his aunt and father dying about this time, he came in for a handsome fortune. He next studied ophthalmic surgery at Guthrie's Eye Infirmary, Warwick Street, Golden Square, and became his teacher's warm friend, taking his side in a then celebrated quarrel with Sir Charles Forbes touching Guthrie's prosecution of the *Lancet*. Thomson used offensive language to Forbes, and a quarrel ensued in which Guthrie would not interfere. The result was a duel, fought on Clapham Common, probably on the south side, where there was a wide extent of secluded ground. So fierce were the combatants that they exchanged four shots before the seconds terminated the fight. In 1827, supported by Guthrie, Thomson became an active member of the Managing Board of the Westminster Hospital. He gave his steady support to the party of Guthrie in the constant feuds that raged between the administrators of the Hospital, and stoutly opposed the old medical interest under Sir Anthony Carlisle, and Messrs W B Lynn and Anthony White. In 1830 he competed against Lynn for the office of Assistant Surgeon, and was beaten; but in 1833, on Lynn's death, he succeeded against John Maitland. He had then married the daughter of Charles W Hallett, the Treasurer, 1831-1845. After his election the feuds of the hospital staff increased, and in 1838 Thomson brought a charge of incapacity against Sir Anthony Carlisle. Sir Anthony was acquitted, and his friends revenged themselves some years later by bringing a similar set of charges against Thomson, who was then full Surgeon. The hospital pupils "were encouraged to bring charges of unskilful practice against him". An investigation, which lasted a fortnight, of charges of incompetence was held before a large committee, and resulted in his being honourably acquitted, though all his surgical colleagues appeared as witnesses against him. Immediately after these events it became his duty to perform lithotomy in their presence. He was in a painful position, but was rescued from it by Robert Liston, who volunteered to act as his assistant in the operation. It was now certain that Thomson could not co-operate with his colleagues without its being extremely irksome to him. He accordingly resigned his Surgeoncy and was elected Consulting Surgeon in 1849. In his profession his fault was excess of audacity, which occasionally made him neglect necessary precautions. As an operator on the eyes he was unsurpassed, and the combined delicacy and firmness of his touch ensured almost invariable success. He published only two courses of his hospital lectures on surgery - on "Diseases and Deformities of the Spine", which later appeared in the *Lancet* about the year 1845. At that time he had during some years devoted his attention to the study of these subjects. After his retirement he engaged disastrously in a speculation called the 'Glass-silvering Company', and sank upwards of £40,000 therein. This affected his health, and he resorted to drugs in order to obtain sleep. Constantly and rashly raising his doses, he succumbed to an overdose of chlorodyne on Jan. 22nd, 1860, and was found by his servant lying on his back dead in his study. In person Thomson was of about the middle height, strongly built, with remarkably dark hair and eyes and a florid complexion. People who knew him little thought him haughty and brusque, but he was a steadfast, generous friend, possessed of great personal courage, and was much beloved by his intimates. He was an early member of the Athenaeum Club, Consulting Surgeon to the West London Institute for Diseases of the Eye, Fellow of the Royal Medico-Chirurgical Society and London Medical Society. He resided at 4 Clarges Street, Piccadilly. He left a widow and several children.