The class L comprised ten 2-4-0T tank locomotives built by the Avonside Engine Co. in 1877. Their boiler was closely related to that of the class F 0-6-0ST, but the addition of a leading axle was intended to improve riding qualities in passenger service. The locomotives were equipped with 3-foot driving wheels and cylinders measuring 10½ by 18 inches. Between 1893 and 1894, seven members of the class were modernised. Three were converted to 4-4-0T configuration by replacing the leading axle with a two-axle bogie, making them broadly comparable to the class L^A. The remaining four received enlarged coal bunkers and a trailing axle, emerging as 4-4-2T locomotives similar to the class L^B.

As traffic demands increased, the class became underpowered for passenger duties and was gradually displaced to secondary work. All seven rebuilt locomotives had been withdrawn by 1939. The three locomotives that retained their original form were sold to the Public Works Department shortly after the turn of the twentieth century. They subsequently passed through several industrial owners before ending their careers at Portland Cement near Whangārei. Remarkably, all three survive and remain operational. The locomotive shown in the photograph is No. 508, originally built as No. 208.