Diesel

Diesel, nicknamed "Devious Diesel", is a sinister diesel shunter and the first diesel engine to arrive on Sodor from the Other Railway. In June 1957 he visited the island. When Diesel came on trial to the North Western Railway, Duck was asked to show him around. Duck took Diesel to the yards, where Diesel claimed to be revolutionary.Duck was unimpressed by Diesel's claims of being "revolutionary" and left him on his own. Diesel was made into a laughing stock by the trucks for trying to pull some rusty old trucks and failing and Diesel blamed Duck for not helping him. Diesel spread fake rumours that Duck had given the big engines rude nicknames. Duck was sent to Wellsworth in disgrace, where he had an heroic inquiry into the matter, but Diesel tried telling lies about Henry. He was found out and sent home in disgrace.

When Duck and Percy needed help at Arlesburgh Harbour, Diesel was the only engine avaliable so he was put on a trial. He was as bad as ever and was sent away for good after shunting some trucks of china clay into the sea, he lost the china clay but the trucks were saved.

When Henry was derailed by some trucks, Diesel was brought back as a last resort to do his goods work, but his attempt to prove his worth resulted in him falling in a barge and he was sent back to the Mainland yet again.

Several years later, Diesel was brought back to help on Thomas' Branch Line whilst Percy was being repaired. Diesel tried to win Thomas and Toby over, without success and after he destroyed several trucks he was to be sent away. However, on his day of departure, Clarabel slipped on oily rails left by Daisy and came off at some points near Dryaw. Diesel, realising that Thomas was blocking his only way home, went to the rescue. Clarabel put in a good word for him and Diesel, although he returned to the Other Railway, was always welcome on Sodor.

Sir Topham Hatt later bought Diesel.