20 King George was the last locomotive to be built at Grand Canal Street railway works[3] though the boiler was made by Kitson & Company.

[2] It is suggested the design might have arisen as an attempt to emulate the success of the LB&SCR I3 class, however on introduction engine No.

20 seemed to have issues with high axle loading restricting the route and it also appeared to have difficulties with heavier trains, steep gradients and hot axleboxes.

The relatively large driver wheel diameter of 6 feet 1 inch (1,850 mm) may not have helped especially as it ended up being used on suburban services, only averaging a mere 90 miles (140 km) a day.

Rebuilds in the 1930s seem to have resolved most of the issues and a 1948 CIÉ report commented: "DSER heavy passenger engines.