Part of the cycle and foot path following the route of the Edinburgh, Leith and Newhaven Railway, and one of a set of four caches I have placed along it. A wee mix of a traditional (Rodney's Burrow), a couple of multi-caches (Bichrist This Tunnel Is Mingin' and this) and a letterbox hybrid (REALLY SideTracked - Trinity Railway Station). The background image to the cache page is some of the graffiti in the tunnel.
I hope that you enjoy the caches.
To find this cache, count the number of small off-white/light grey boxes along the top of the tunnel. This is CD. I'll use different letters to those in the "Bichrist" cache, in case people are looking for both of these at the same time.
Then, go slightly outside the north entrance to the tunnel and look at the stone wall around the tunnel entrance. There is a sign up and to the left of the tunnel entrance. The number of colours on the sign is E. The number of letters in the first word is F, the number of letters in the second word is G.
The cache is located at N 55° 58.(C*E)(E+F)G' W 3° 12.(C-1)FE'