Robinson developed these heavy GCR class 9N tank locomotives for fast suburban traffic. With a driving wheel diameter of 5 feet and 7 inches or 1,702 mm and three coupled axles, they were also able to achieve good acceleration. Otherwise they were state-of-the-art with piston valves and superheaters. Between 1910 and 1917, 21 locomotives were built in GCR's Gorton works.
The second production lot was delayed until after the First World War. In 1923, ten more were built with adjustments by Gresley, including a smaller heating surface. These were now being built by Hawthorn, Leslie & Co. as were the next 13 in 1925 and 1926.
The previous class 9N became the A5 at the LNER. In order to be able to distinguish the first and second series, these became the A5/1 and A5/2. British Railways took over 43 of 44 locomotives. The rest were retired between 1957 and 1960.