Wallace Brian Vaughan Sinclair (27 September 1915 - 13 December 1988), universally known as Brian, was a British veterinary surgeon who worked for a time with his elder brother Donald and Alf Wight (better known under his pen name of 'James Herriot'). He worked as a student vet employed by his brother, until graduating from the Royal (Dick) Veterinary College in Edinburgh in 1943, subsequently joining the Army Veterinary Corps in India. On demobilisation, he joined the Ministry of Agriculture's Sterility Advisory unit, rising to become head of the Veterinary Investigation Centre in Leeds.
He was the model for the character 'Tristan Farnon' in Wight's semi-autobiographical novels, which were later adapted to the big screen in two films, and television under the name All Creatures Great and Small.
Unlike his elder brother, who for some time saw the books as a great trial of his friendship with Wight, Brian made no objections to Wight's ne'er-do-well portrayal of him, and in fact seemed rather to enjoy the celebrity, appearing on television and lecturing at veterinary schools all over the UK and elsewhere.