Born at Stamford, one of a large family. His father educated his elder brother, Edward (qv), for the medical profession, but had no thought of doing so in the case of William, who only attained his object by dint of indomitable perseverance. He was educated at Christ's Hospital, first at Hertford and then in London. He was apprenticed to an apothecary in London, and often used to tell of the rhyme with which he would be taunted by the street boys: "O salts and senna, you would not do for me;/ I'd rather go to Jericho than a doctor's boy I'd be." He had not much spare time and very little spare cash, but he used often to employ his meal-times in running to a library for books in order to improve his education, and had to buy his own candles in order to sit up to read them. Gibbon, Grote, and Adam Smith were authors whose works were devoured by young Clapton; his memory was so retentive that he could repeat the whole of *Paradise Regained*, as well as the whole of the Psalms in the Prayer Book version. Thus, by pluck and perseverance he prepared himself for a professional career, and eventually entered St Thomas's Hospital, then situated at London Bridge Station. He was a successful student and became Resident Accoucheur and Assistant Resident Medical Officer. Soon after qualifying he settled in practice in the City, living for most of the time in Queen Street, with addresses in Bloomsbury. He was for many years Medical Officer of the British Equitable Assurance Company. He was appointed Surgeon of the West City Dispensary and Royal Humane Society, and was also for a long period Secretary of the City of London Medical Book Society. A sociable man, with many friends, he identified himself with the interests of the profession in the City, and was active in civic affairs. For ten years he represented the Vintry Ward in the Court of Common Council (1872-1882). Retiring from practice some few years before his death, he settled at Canterbury, where he loved to attend the cathedral services for the sake of the music. He was for some years churchwarden at St Stephen's Church, Canterbury, and took part in much social and philanthropic work to within a few weeks of his death, which took place on August 20th, 1912, at his residence, Rose Villa, St Stephen's Road.