Zillertal was one of two U-Class 0-6-2T locomotives built in 1900 for the opening of the Zillertalbahn in Austria by Krauss & Co. The Zillertalbahn runs nearly 32km from the mainline at Jenbach to its terminus at Mayrhofen. Two other steam locomotives operate a mid-day heritage service on the line, alongside regular diesel railcar services.
The U-Class has been under major overhaul and was first steamed successfully on 24th May 2019. In June representatives from the W&LLR’s mechanical engineering department travelled to Austria to observe further testing, which proved equally successful. The locomotive arrived in Wales on hire from the Zillertalbahn on 13th August 2019 and entered service on 30th August, running at times with former Zillertalbahn carriages which arrived on the W&LLR during the 1960's and 1970's.