The DH class of Northern Ireland Railways consisted of three diesel-hydraulic shunting locomotives numbered 1, 2 & 3.

They were of 0-6-0 wheel arrangement and fitted with Dorman 12QTV engines of 620 hp (460 kW), connected to an EE Twin Disc torque converter and a Wiseman final drive.

The locomotives were of EE's standard 'Stephenson' class, and were obtained primarily for shunting work, trip freights and engineer's trains.

2 suffered a catastrophic engine failure on Saturday 9 September 1989 (the day before the excursion),[1] despite having been overhauled by NIR at York Road Works.

2 and 3 ended up in secure storage at Larne Harbour, where the Diesel engines, torque converters and final drives were removed in 1991.

In September 1994, the Irish Traction Group purchased the three locomotives from NIR and moved them south to their restoration base at Carrick-on-Suir.

When they moved to Carrick-on-Suir by rail, they formed the last recorded un-braked train in Ireland and were regarded as an "Engineers Special".

Unfortunately, despite the best efforts of the ITG to prevent the locomotives from being vandalised while at Carrick-on-Suir, they were repeatedly attacked during their ten years of outside storage.

This has prompted the ITG in recent times to construct large metal covers to protect any engines stored out of doors at Carrick-on-Suir, both from vandals and deterioration caused by the Irish weather.

In 2005, the ITG was approached by Beaver Power Ltd, who wanted to buy the three locomotives for re-use in Sri Lanka.

This locomotive had lost its engine, torque converter and final drive in 1989, and was heavily stripped due to its use by Beaver as a spare parts unit.