'Terry', as his mother called him in her RA portrait (1913), was the son of Cyrus CUNEO ROI and Nell Marion CUNEO (nee Tenison), and born in Shepherd's Bush, London. He showed artistic talent within an artistic family from an early age. Initially tutored by his mother, he began formal training at Chelsea Polytechnic (1924- 27) under Percy Jowett, who considered him singularly unpromising as an artist; later in life he attributed the greatest influence upon his work to his father.

His work is first mentioned in Cornwall when he exhibited linocuts at STISA in 1925. He was most active as an illustrator in the 1930s, his first successes being commissions from Chums, followed by Boy's Own, The Magnet, Christian Herald, and Wide World Magazine, Strand and especially the Illustrated London News. In 1931 he joined the London Sketch Club and by 1938 STISA, by which time he was writing and illustrating his own stories.  He was the official artist for the coronation of Queen Elizabeth II in 1953.

He is now hailed as the greatest railway painter of the twentieth century, and known for his paintings of historic groups, battles and parades. At the RCM, Truro, is a collection of six of his oil paintings focussing on the industrial history of Cornwall.