Clyde Engineering delivered the first locomotive in April 1912 and by November 1917, a total of 190 were in service.

There was a problem with the locomotives being unbalanced, causing speed restrictions to be imposed to avoid rough riding and track damage.

Following further investigations, 24 of the class received balanced coupled wheels and these were permitted to operate at higher speed on mail and fruit trains.

In the later period of their lives, the majority were fitted with larger turret type tenders.

In later years some were used as heavy shunting locomotives and from 1963 on some of these had automatic couplers fitted to the front.