Two 'Funkeys' were purchased in the mid 1990's to augment the Ffestiniog Fleet and prepare for the expansion with the set up of the WHR(C). The other vehicle is Vale of Ffestiniog - which received a heavier rebuild.
Unlike other larger diesel locomotives, this vehicle is named in Welsh only, after Caernarfon Castle which is in view of the WHR(C) Northern Terminus.
Castell Caernarfon is a 27-ton turbo-charged B-B diesel-hydraulic that was built by CH Funkey & Co (Pty) Ltd of Alberton, near Johannesburg, South Africa, for a diamond mine in Namibia. It arrived at the FR on 16 October 1993, purchased from Pretoria Portland Cement Ltd, New Brighton Cement Works, Port Elizabeth, Cape Province.
The loco is fitted with a turbocharged 335hp Cummins engine, making it one of the most powerful narrow gauge diesels in the UK. After arrival at Minffordd Yard it was first known as "Funkey 2" and was overhauled at Boston Lodge in 1995-6. Prior to taking up duties for the WHR(C) it was placed on display in July 1996 at Gwyl Caernarfon Festival (during which a naming ceremony took place). It became the first locomotive to be moved to Dinas, in January 1997, and took part in that month's construction launch ceremony.
Castell Caernarfon can be seen more often on offpeak workings, but can be called on the occasions when no steam loco is available.
For the 2000 season, the livery was amended slightly, with the addition of "cat's whiskers".
Having given eight years of trusty and reliable performance from arrival, heavy maintenance was undertaken between January and April 2005. Castell Caernarfon is the only diesel capable of hauling a full passenger service over the WHR(C) route, and as such can be called upon for "Thunderbird" duties should it be required.