Thomas Lambert Oldfield studied at the New Veterinary College and School of Medicine in Edinburgh, but was not qualified as a veterinarian when he arrived in Natal with the 6th (Inneskilling) Dragoons in 1881. Ranked as a veterinary corporal he was appointed as assistent to the inspecting veterinary surgeon of the British troops. He relinquished this post in 1884. In 1892 a pamphlet on the foot of the horse was published in Wynberg (Cape Town) under his name. Its somewhat disjointed title was: Diseases of the foot: Some of the causes, description, and treatment.- Remarks on shoeing.- The shoeing forge.- Its relation to the veterinary surgeon.... That same year, in a letter to the Natal Mercury dated 9 November 1892, he wrote about glanders, stating among others that "Glanders... is a specific febrile disorder peculiar to solipeds, and is capable of transmission to man and other animals". His letter was reprinted as a six-page pamphlet, Glanders and farcy... in Durban. In 1896 he applied for an appointment as inspector of imported cattle at the Point, Durban, but was employed as inspector of slaughter houses.
In 1905 Oldfield sat for the Natal Veterinary Board's examination in veterinary medicine and surgery at Allerton Laboratory, which enabled him to register as a veterinarian on 12 April that year, under Act 21 (1899) of Natal. He was only the second candidate in South Africa to pass a local veterinary examination. After registration he practiced as a veterinarian in Berea road, Durban, until his death in 1921. In 1897 he was secretary of the Ex-Cavalrymen's Patriotic and Mutual Aid Association. In the Natal who's who (1906) he described himself somewhat pompously as "Fellow of the Royal Society of St George of England, past Grand President Sons of England Patriotic and Benevolent Society. Founder of Durban Branch of the Society for the Prevention of Cruelty to Animals." He was survived by his wife, Annie Oldfield, born Fraser, with whom he had four children.