Duke was built at Boston Lodge at Minffordd, Wales to the order of John Arnold Norramby, Earl of Sodorand chairman of the MSR, in 1879 for the opening of the Mid Sodor Railway in 1880. The Board of Directors named him in honour of the Earl and rostored him to haul the Opening Train. He worked with several other engines on the Mid Sodor, including Falcon and Stuart (later named Sir Handel and Peter Sam respectively).
Soundly built, Duke was well maintained and kept in service until 1947 when the railway closed. While Stuart and Falcon were sold, no buyers were interested in him, so he was left oiled, greased and sheeted up in Arlesdale Sheds, where he was all but forgotten. He believed that the Earl would come to rescue him, but as time went on, he did not show, and Duke began to have doubts which grew stronger and stronger. He was unaware the Earl he knew he had been killed during the Second World War, and that his successor was just a boy, who did know of Duke.
- Season 4 - Granpuff, Sleeping Beauty, Bulldog, You Can't Win!, Rock 'N' Roll (cameo), Special Funnel (cameo) and Steam Roller (cameo)
- Season 7 - Harold and the Flying Horse (stock footage cameo)
- Season 24 - Smudger's Adventure (flashback; stock footage; does not speak)
- Season 27 - Diesel of the Railway (mentioned), Peter Sam's Patience (mentioned; flashback), Dusty Rusty (cameo), Recoveries, Peter Sam's New Funnel, Mighty Mac and the Campers (cameo), A Special Return (mentioned) and Freddie's New Whistle (stock footage; mentioned; flashback)