This is the currently inaccessible triple deck tunnel, which runs right up to this part of the site from the stable yards, only interrupted by the railway cutting. It ends roughly where it ends on the plan, meeting up with the Great Tunnel. Just behind the house, among the overgrowth, there appears to be a collapse in the ground, suggesting that the upper tier of the triple deck tunnel has partly collapsed at this point, but at least proving that it's there!

Click anywhere in this window to close it