That my friend is a very good question. It's not a tunnel like the wormhole caves (carved out of sandstone). The vaulted ceiling give it the feeling of a priest hole. I'm not sure if you are familiar with New Brighton, but we live over the road from New Brighton Battery. The entrance to our cottage is up a narrow path, and along this path (next to our garden) is 5 narrow sheds. It's stated on a website called 'History of Wallasey' that these sheds used to be Officer's Toilets from The Battery. I suspect that before being bricked-up, the tunnel may have led to The Battery? The area we live (Magazine Brow) is famous for it's history of Smuggling, and not too far along the promenade was a famous house called Mother Redcaps that was a known Smuggling Den.