Merstham Tunnel, photographed on 25th August 2007. photograph by Gregory Beecroft

This is the south portal, which has a prominent stone capping and string course. The capping is bracketed out over the pilasters. A brick arch with a keystone is quite unusual.

Merstham Tunnel sighting tower. photograph by Gregory Beecroft

An exceptional feature of this tunnel is the brick sighting tower, which was constructed to give surveyors line of vision over the hill when setting out the railway. These were normally temporary structures and it is most unusual for one to have been built so solidly and still to be standing. It is located in the fields over the tunnel.