The Kettleness tunnel is located inland and is now hidden from plain sight within farming fields, but it’s there if you take the time to look.
We found two tunnels leading from each other, the first tunnel is roughly 250 metres long while the second tunnel is a good mile long. Both tunnels are blocked by a wall that’s roughly 8 feet tall so the adventure involved some climbing. Once you come to the end of the first tunnel, over the wall, you are presented with an overgrown area where the track has been removed at the cliff edge that has fallen into the sea before you come to the entrance to the Sandsend tunnel.
The Kettleness tunnel was built in the 19th century with the aim of re-routing the Middlesbrough to Whitby to Scarborough rail so that it was away from the edge of the cliff. The tunnel is now way over 100 years old and was closed in 1958 and has been abandoned ever since. Considering how old and neglected the tunnels are they are in pretty good shape inside with nature slowly taking back the land via weathering.
The deeper you get into the second tunnel the darker, warmer and wetter things get; after all you’re walking underground. There are a number of air tunnels leading up to ground level which are all dripping with water and full of wet clay.
This is how the outside of the tunnel looked in the 1950s:
And this is how the tunnel looks now: