Derek was built by the Clayton Equipment Company and Beyer, Peacock & Co in 1963 and worked on the other railway for a few months until The Fat Controller needed an engine to help BoCo and the twins. On his two first days he broke down on Gordon's hill and BoCo came with some workmen to the rescue and again when he was the banker for Bill and Ben's train. The Fat Controller soon sent Derek to the works to be mended. Later Derek returned from the works and soon became a resident of Edward's line.
Later Derek was teased by Arry & Bert for his troublesome engine but the tables turned when Bert's engine broke down and Derek had to help get the stranded train to the docks on time. As an reward The Fat Controller decided to send Derek to the works again but this time for an overhaul and Edward arrived to take Derek who was very happy on having his engine troubles sorted out at last!
Derek is one of most polite, jolly and optimistic diesels on the railway, he's highly enthusiastic about his work and tries to look on the brighter side of things, Even if his engine breaks down it doesn't let him ruin his mood. He has made very close friendships with many of the engines especially BoCo, Edward, Bill, Ben, Neville and Bear.