Born about 1778, he was educated in England. Going in 1794 to Calcutta, where his father was living, he had a subordinate post in a public official[clarification needed] but gave it up for an ensigncy in the 76th (Foot) Regiment. Promoted into the 74th Regiment, he served in the Fourth Anglo-Mysore War under General George Harris, and in the Second Anglo-Maratha War campaigns of 1803–4. He was distinguished also in the battle of Assaye.
In 1805 he sold his commission, and, visiting an uncle, Samuel Tolfrey, in Ceylon, obtained a post in the public service there in 1806. In 1813 he was assistant commissioner of revenue and commerce, and shortly afterwards proficiency in Sinhalese obtained him the post of chief translator to the resident at Kandy. On the arrival of Sir Robert Brownrigg as governor in 1812, a Bible society was started, and Tolfrey undertook the revision of the old Sinhalese translation of the Bible made by the Dutch. Tolfrey died in Ceylon on 4 January 1817.
An early English student of classical Pali, Tolfrey found the existing Sinhalese Bible translation too colloquial, and translated each verse into Pali as he worked. At the time of his death, he had nearly completed the translation of the New Testament into Pali, a work which was subsequently printed. Benjamin Clough used Tolfrey's materials for the compilation of his Pali grammar, produced in 1824.
- The Gentleman's Magazine: p. 185, 1818 "William Tolfrey. Died at Colombo, in Ceylon, Mr. William Tolfrey. He was suddenly attacked by a violent disorder, which in less than a fortnight carried him off on 4th Jan. 1817."
- Language, religion, and ethnic assertiveness: p67 Kē. En. Ō Dharmadāsa – 1992 "In connection with the latter there were first the Bible translations undertaken as part of Evangelical activity. The first Bible translation into Sinhala in British times was by William Tolfrey, the Old Testament in 1819 and the New ..."
- Dictionary of National Biography. London: Smith, Elder & Co. 1885–1900. .