The A2 was a Pacific express locomotive designed by Vincent Raven for the North Eastern Railway shortly before the grouping into the LNER. It was based on the class Z Atlantic with an additional driving axle and a longer boiler with a wide firebox. At six feet, the diameter of the boiler was the biggest in Britain, together with Gresley's GNR class H4, the later LNER class K3. Two were built in 1922 at Darlington of which only the first one was actually steamed up before the grouping. Three others followed in 1924 which were directly delivered to the LNER.

At the same time, Gresley had designed his A1 Pacific for the Great Northern. Direct comparisons between both classes showed that the A1 was more powerful and technically more advanced in general. Additionally, the A2 had a longer wheelbase, what possibly limited the suitability for some lines. Ultimately, as Raven reached his retirement age and Gresley became the chief mechanical engineer of the grouped LNER, his A1 was chosen as the new standard express locomotive.

The five A2 locomotives were numbered 2400 to 2404 and named after cities. In 1929, Gresley rebuilt 2404 with a taper boiler that had a reduced pressure of only 180 instead of 200 psi. As this did not deliver considerably more power, no others were rebuilt. When they needed repairs in the thirties, it was decided to rely on the greater number of A1 locomotives. So all five A2 were withdrawn and scrapped in 1936 and 1937.