Train passing through Mickleham Tunnel, Surrey, England. The railway between Leatherhead and Dorking, opened by the London, Brighton & South Coast Railway in 1867, follows the Mole Valley through the North Downs. The Mole river meanders to the east at Mickleham, but the railway passes through Mickleham Tunnel to avoid this deviation. The tunnel is 524 yards long. The southern portal is appreciably more ornate than the northern one, with triangular flint panels in the spandrels and stone decoration. Landowners often required ornate designs for structures in return for withdrawing objections to construction of the railway through their estates.