The Festiniog & Blaenau Railway was of 1' 11½" gauge and was of 3½ miles length and opened in May 1868. It was purchased on 13 April 1883 by the Great Western Railway. It was later converted to standard gauge as the extension of the new Bala & Festiniog Railway. Two locomotives were taken over, both being built by Manning Wardle.
References
Festiniog & Blaenau Railway Wikipedia(Text) CC BY-SA