My raised beds are made of railway sleepers; given that you can tell they have really been used as such, and they are both narrow gauge a normal gauge, I assume they came from the environment here. There were both type of railroads going from the village in the direction of Bangor. But that also means that must be quite old. These railways were built in the 19 century! So no surprise that they are deteriorating a bit.
I had already been replacing rotten ones with stone. And during the barbecue, another one died. So I had to snap into action again! And this was right by the river, where all stonework is slate, so I decided to replace the sleeper with slate as well. And that worked out. It should be sorted for centuries now again!