The A4 is a truly iconic locomotive in every sense, instantly recognisable by millions regardless of their own railway company allegiance. Its shape is unique, its performance legendary, there is simply no other engine like it. In the 1930s, when the A4s were built, speed was king. Everyone wanted to go faster and Gresley designed the A4 for long distance speed, with elegance. The streamline shape was in vogue; cars, planes, buses, even caravans,  though in reality it only became effective at higher speeds, say over 60 mph. When Mallard broke the world steam record in July 1938 with 126 mph its place in history was assured.