After the five Leitrim class locomotives from the 19th century, SL&NCR had procured three more Sir Henry class locomotives in 1904, 1905 and 1917, which also had the 0-6-4T wheel arrangement and were manufactured by Beyer, Peacock & Co. After the Second World War, the existing fleet of vehicles was no longer sufficient and in poor condition, so that the procurement of a powerful Garratt locomotive was initially considered. The route was now between Ireland and Northern Ireland, which made operation not exactly easy. In addition, it was in a sparsely populated and not very prosperous area, which significantly worsened the financial situation and made it impossible to buy an expensive locomotive.

Finally, two smaller locomotives were ordered, which again had the 0-6-4T wheel arrangement and were completed in 1949. Since the SL&NCR could not pay for the locomotives, lengthy negotiations with the government of Northern Ireland followed. It was finally agreed on a lease purchase and the locomotives were used until the line was closed in 1957. They were named after the lakes Lough Melvin and Lough Erne, which explains the name of the class. They were then sold to the Ulster Transport Authority and used by them as Class Z for about ten years. Preserved by the Railway Preservation Society of Ireland, Lough Erne is now at Whitehead on the Northern Irish coast.