The term "Deltic" refers to a type of diesel engine known for its unique design, featuring a two-stroke cycle and opposed pistons. This engine was developed in the 1950s by Napier & Son and is notable for its high power output and efficiency. Deltic engines were primarily used in railway locomotives, particularly in the British Rail fleet, where they became famous for their distinctive sound and performance. Deltic locomotives, such as the British Rail Class 55, were introduced in the 1960s and became iconic in the UK rail system. Their design allowed for a lightweight structure while delivering impressive speed and acceleration. The Deltic's engineering has influenced various applications beyond rail transport, showcasing its innovative approach to diesel engine technology.