If he became an engine driver with a mainline railway company then he must have become an engine cleaner before his 25th birthday.Promotion to driver was strictly on length of service in the fottplate line of promotion. i.e. engine cleaner, cleaner passed for firing, fireman, fireman passed for driving, and finally driver. Usually in that era after several years service. My father entered service in 1919, and became a driver in 1942 thanks to the wartime surge in traffic. I believe it is therefore much more likely that he was a stationary engine driver, or a driver on a steam traction engine which were quite common in the early 20th century.
