A (quite obscure) question for the railway historians out there - just to the south of Merstham tunnel (near Redhill, Surrey), the railway is in a deep cutting which lowers as it approaches the M25 bridge. A short distance north of that bridge, on the eastern side of the line, there is what looks like the remains of a very old side cutting, now heavily overgrown and partly filled in with soil, etc. Looking at maps, this appears to lead across to the Quarry line cutting, which was built after the original Redhill route. My question is; does anyone know if this was either a rail or roadway connection built to facilitate the Quarry line construction, or is it simply a natural/unrelated formation? I have found no specific reference to it anywhere so far.