As promised, I have done some research!
(Incorrect research though… – view Not a Fowler Dock Tank! for more detail)
LMS “Fowler Dock Tank”
This train is the LMS Engine No.68478, commonly known as a Fowler Dock Tank, used to shunt in docks, designed to go around tight curves. Only ten were built, between 1928 & 1929. They were all decommissioned and scrapped between 1959 & 1964, which is sad because none were preserved in museums. Although it fits in the time period, it doesn’t fit with the inland setting of the model.
My model LMS “Fowler Dock Tank”: