The locomotive was built at the Tubize workshops in Neville, Belgium in 1948 and brought by the Jokioinen Museum Railway to replace  their newest and most powerful Herschel locomotive which had to be given to the Soviet Union because war payments to Finland were late. Number 5 was used along with its sister locomotive number 4 to haul goods trains on the Jokioinen Railway until the 1960's and until 1951 also pulled passenger trains. Number 5 was withdrawn from service on the Jokioinen Railway in 1964 due to cracks in the firebox and until 1972 it was placed on a section of track and a small shed was built around the locomotive at Jokioinen station.

In 1972 the locomotive was brought by Englishman who aimed to renovate the locomotive and return it to steam once again hauling trains in the UK and it was shipped to the UK on a ship. However the owner had to give up the locomotive and the Tubize locomotive was brought by the Welshpool and Llanfair Light Railway in 1983 and it was delivered to the Llanfair station headquarters by road on the 28th September 1983.

The locomotive was then put on display outside Llanfair station for funds to be raised for the major overhual which would see the locomotive return the big tank locomotive to steam on the line. in 1993 the locomotive was moved into the railways workshops at Llanfair station and was stripped down ready for the major overhaul to start to restore the locomotive to steam alongside the railways steam fleet.

During the overhual of the locomotive many feature were altered on the locomotive which included a shorter chimney and the moving of the safety valves from the boiler to the top of the dome on the boiler of the locomotive. Also the locomotives two whistles were moved to the front of the cab.

Also the boiler was removed and sent away for the cracks in the firebox to be repaired and also the fitting of new fire bars in the firebox which were farther apart then original but would produce good steaming while in service on the line.

After the completion of the locomotives overhaul there were a number of test runs over the 8 mile line to check everything on the locomotive was running ok and at this time the was still in undercoat. The locomotive finally made it to Welshpool under its own steam on the 15th April 2000 in a very unpleasant snow storm and the locomotive made several further trips to Welshpool with different loads to allow the big locomotive to run in after its overhual.

On the 19th May 2000 the railway inspector visited to inspect the locomotive and then do a return trip to Welshpool with a load to allow the inspector to see if the locomotive can be passed for passenger service. After returning to Llanfair the inspector gave his approval for the locomotive to enter service on the Welshpool and Llanfair Light Railway but the big locomotive would have to wait a further couple of weeks until written approval arrived by post before it could haul its first passenger services.

On the morning of the 2nd June 2000 the workshop staff hade lit up the locomotive with the hope that the locomotive would do its first passenger trip to Welshpool and return. The written approval arrived in the post that morning so then the task of preparing the locomotive for the 16:15 train to Welshpool and return.  The locomotive was ready by 15:45 and once the lunchtime train arrived from Welshpool the locomotive was coupled to the train ready for departure to Welshpool with its first passenger train. The locomotive put in a strong performance on its first passenger run to Welshpool and arrived in Welshpool on time and with a train fully loaded with passengers

After its first passenger turn on the Welshpool and Llanfair Light Railway the next task was to get the locomotive crews familiar with the locomotive as it was a lot bigger and different compared to the small tank locomotives the railway operates. The locomotive was used a lot during its first year on the railway hauling many passenger trains over the 8 mile line.

The locomotive was later found to be to heavy for the Welshpool and Llanfair Light Railway and was took in the workshops at Llanfair to have a few modifications which would stop the loco holding full tanks of water and a bunker full of coal in an attempt to reduce the weight of the locomotive.

The locomotive was found to be still heavy after these modifications and was only run on the line at every Annual Steam Gala weekend when it was needed to haul passenger trains. But talks were in progress with the Jokioinen Railway in Finland to return the locomotive to its home line and back alongside its sister locomotive.

At the railway Annual Steam Gala weekend in 2009 officials came from the Jokioinen Railway to inspect Orion and to ride on the locomotive during the weekend and also to see the W&L tanks in operation over the weekend. On the Sunday of the Gala it was announced that Orion had been sold to the Jokioinen Railway and that the Gala would be the last time to see the big tank locomotive in steam.

After the Gala weekend the locomotive was got ready for transportation to Finland and this involved the coal bunker being empted and water tanks drained and the grondana couplings removed from the locomotive. The locomotive was loaded onto a low loader at Llanfair for the journey back to its original home in Finland where it would be reunited with the sister locomotive No. 4 on the Jokiosten Railway Museum.

Since No. 5 Orion arrived back in Finland after the long sea journey from the Welshpool and Llanfair Light Railway the locomotive has had a lot of modifications to bring it back to its original appearance and to make it appear the same as the sister locomotive No. 4. Both locomotive almost look alike and there are ways to tell between Orion and the sister locomotive No. 4 by the nameplate and the smoke box door style.

Some Pictures of the modifications made can be found below and you can also see how the locomotive has changed in appearance since arriving in Finland after Leaving the UK