After a series of trials throughout the North East Area, all of the remaining H1s were rebuilt as A8 4-6-2Ts between 1933 and 1936. During the process of rebuilding, the boiler was modified to include a Robinson-type superheater rather than the original Schmidt superheater. In 1935, further modifications resulted in the A8 boiler being interchangeable with the A6, A7, A8, H1, and T1 classes.
The rebuilt A8s could easily work the heavy suburban traffic and long distance coastal trains on which they were put to work. They were also welcome replacements for the ageing G5 0-4-4Ts which had been working these services. Allocations of the 45 locomotives were split between the North East / Newcastle area, the Yorkshire Coast Whitby and Scarborough, Hull, and Leeds (Neville Hill).