- "Duke is the kind to exert authority... Of course he deserves respect; saved my bunker a few times..."
- ―Sir Handel, Blunderbuss
Long ago, Duke worked on the Mid-Sodor Railway with Falcon, Stuart, Fearless Freddie, Smudger, Stanley, and the Scrap Engine. Sometimes they doubted Duke because of his age, but he always proved his worth. He rescued Falcon from almost rolling down a mountain, showed Stuart that he had the strength to carry the train home even when he had broken down, and tried to keep Smudger and Stanley out of trouble. They worked happily together for many years until their line was closed down. Stuart and Falcon were sold to another railway, and Duke was left alone in the shed. Many years later, a rescue party was brought together to find him, and with a great deal of determination, they succeeded! The team brought Duke to his new home, the Skarloey line, where he was joyfully reunited with Stuart and Falcon. Fearless Freddie returned some years later, but Smudger had been turned into a generator, and would never be able to join them.
When Luke was brought to the Railway and hidden in the Blue Mountain Quarry, Duke refused to work there until Skarloey and the others told The Thin Controller the truth. He thought that he had "much more integrity than living with a grand old lie." After Luke could come out of hiding, Duke eventually gave in and now works there from time to time.
Duke was sent to the Mine Junction to help Bertram, and quickly became popular among the other engines with his stories about Smudger. Bertram, however, had a tendency to barge in and be a monumental buzzkill, which infuriated Duke to no end!
Duke's favorite shed was destroyed after the Thin Controller decided to store ancient gunpowder there for safe-keeping. The inevitable explosive incident was mostly Bertram's fault, and Duke is still very upset with this unfortunate happenstance.
During a massive windstorm, Duke had a bit of a senior moment, forgetting that Young Ivo Hugh was still at the top station with a full train!
A kind soul, Duke happily welcomed Rosie to their transfer yard, but not before curtailing Bertram's lengthy introduction!
Duke often tries to make speeches at celebrations, which are happily received by Peter Sam and Ivo Hugh, but not many others.
Later, with Skarloey and Rheneas working the passenger lines, Duke was the engine in charge of the BMQ, and he soon began to boss Paxton around when the diesel returned to the quarry. He scolded Paxton for taking too long shunting, with Thumper reprimanding him for it, though Duke took no notice from Thumper. When Rick Shay and Weaver came about wanting to learn about the Thin Controller's fencing lessons, Duke told them that it was best not to carry around firearms around the quarry, but was civil to the two and warned them of the blasting operations. Sir Handel then came along and began to tell Duke off for idling, though Duke defended himself saying that he was just setting the two rangers straight. However, when Rick Shay accidentally blew up some dynamite intended for blasting, Duke was derailed, but escaped the worst of the blast, which could not be said for Sir Handel, who was partially buried under the rocks.
Later, at Crovan's Gate Works, after being taken there for repairs, Duke encountered Arthur, who was still being mended after the Munitions Incident and comforted Sir Handel, who was griping endlessly after the explosion. The next day, Duke was pacing around the works in order to see how his repairs were going along, but after Paxton brought over Vegard, and Rusty came in with some supplies (Blowing his new two-toned horn in the process), Vegard accidentally misfired, startling Duke's driver and fireman, causing them to tumble out of Duke's cab, leaving Duke to run through a wall. After Paxton went to check on him, Duke admitted that Paxton was not the deliquent that he though he was, though due to the accident, he had to stay on at Crovan's Gate for a little longer.
Despite falling asleep during auditions, Duke is cast as Claudius in the Skarloey Railway's production of Hamlet. He is kept up at night by Freddie, who was practicing his role as Polonius, leaving him quite inspired for his performance as Claudius.
Duke is compassionate, wise, and stubborn. He likes to keep the younger engines in line and impart them with words of wisdom. He insists on doing things his way and will not tolerate foolishness from the younger engines. He is a brave engine and wants what's best, but he as not aged the most gracefully. The hierarchy of the railway is not to Duke's liking, because Skarloey and Rheneas see themselves as the examples that should be followed. Duke has taken Ivo Hugh under his wing, seeing him as phenomenal teacher. This thus fits him into the category of being the "Grouchy Old Man" of the railway.
Duke absolutely despises Bertram, who more than often inadvertantly ruins a passionate recollection of his past, and he also possessed a dislike for Paxton, thinking that he is "Unruly" along with Bertram. However, after Paxton showed a great deal of compassion and worry for Duke after the latter had been damaged in an explosion, Duke warmed up to Paxton a great deal. Duke is also a victim of chronic narcolepsy, as he falls asleep often while having conversations with the other engines.
The other engines sometimes hear Duke crying out in the middle of the night. Sometimes the name "Smudger" is heard.
- Season 1: Lift Bridge (cameo), The Old Warrior, Double Whammy, Cannon Fodder (cameo), Greg and Lars (cameo)
- Season 2: Two Hearts Burn Together (cameo), Mavis and the Tornado, Rosie, Just Another Wild Goose Chase, Munitions (cameo), Blunderbuss, Luke and Millie's Blue Mountain Adventure (mentioned), Aura of Menace (cameo), Henry and Kurt (cameo), All the World's a Stage, Swashbuckler
- Season 3: Samson, BoCo, and the Man in the Hills (cameo), Culdee Fell (cameo), Chivalry is Dead (cameo), Percy and Asbestos (cameo)
- Duke's 2009 re-release model has been used since Blunderbuss.