Deltic locomotives are a type of diesel-electric train engine that were first introduced in the 1950s in the United Kingdom. They are known for their distinctive design, featuring a unique Napier Deltic engine with two banks of cylinders arranged in a triangular configuration. This design allows for high power output and efficiency, making them suitable for fast passenger services. These locomotives were primarily used by British Railways and became famous for their speed and reliability on mainline routes. The Deltic class, particularly the Class 55, is celebrated among train enthusiasts and remains a symbol of British railway engineering.