Authorised by a Parliamentary Act of 1865, the Ross & Monmouth Railway followed the Wye Valley for 13 miles, crossing the river twice and forging short cuts through two rocky outcrops with tunnels. The lesser of these, at 433 yards, emerged at its west end into Symonds Yat, a loose community of dwellings bisected by the Wye. The first trains passed through on 4th August 1873. Ten months later, Monmouth Troy Station became the line's western terminus after a third bridge over the river was completed.Built by contractor John Firbank, the tunnel curves to the south throughout on a radius of around 14 chains.
The east portal is minimalistic, pushed into the rock face at the end of a short, steep-sided cutting. It is stone-built except for a string course of brickwork around the voussoirs which helped to deflect water running down the spandrels.The bore itself is horseshoe-shaped in profile, with stone sidewalls and a brick crown. The platelayers' safety was provided for by the inclusion of generous refuges at both sides. The tunnel is in fair condition and mostly dry.
Today, an assortment of cables, lights and junction boxes are apparent in the darkness, the reasons for which are not immediately clear. The western end looks out into the grounds of a hotel where some some infilling of the approach cutting makes the portal appear smaller than it actually is. The design is similar to that at the east end.Whilst the through route - including the tunnel - closed on 5th January 1959, the northern section of line remained operational until November 1965 to serve the AEI cable works siding at Lydbrook Junction. By the summer of 1967, the tracks had been lifted.