Gwydion worked on the Cynwrig Railway alongside Bertram till the death of their controller, Ellis Garth. The railway was subsequently closed and, despite Bertram's pleas to Caderyn Gerralt to purchase him, Gwydion was left behind.
Gwydion is old and wise with a old school sense of humour. He was very close to Bertram, the latter constantly referred to him as their best friend.
- Behind the scenes, Gwydion shares a face mask with Hywel.