At each cache there is a logbook with a letter on the back. By collecting all of the letters you are able to complete the puzzle for the bonus cache – The Cambrian Trail Bonus Cache. This cache is big enough for some small swaps and trackables.
The Railway Line is the first and (at time of placement) only line in the whole of the UK (apart from the Eurotunnel) to not have any signals along it. That means no semaphore signals, no lights, nothing. The signal boxes are no longer there and all of the trains along it are signalled with the aid of some technically minded people in a room full of blinking lights in Machynellth.
This cache is a small cache with easy parking nearby.