Railway tunnel portals MVL3/41, west end of Standedge Tunnel

The west end of Standedge Tunnel features three railway tunnel portals. The central portal was constructed between 1845 and 1849 by contractor Thomas Nicholson and engineer Alfred Stanistreet Jee for the Huddersfield & Manchester Railway line. The south portal was built at the same time, in advance of a tunnel excavated between 1868 and 1871. The north portal was built later, between 1890 and 1894, for the London & North Western Railway.

The portals are made of brick or gritstone arches, with coursed and squared quarry-faced gritstone walls and ashlar dressings. They are located in a deep cutting next to Station Road in Diggle. The central and south portals share a matching design, each featuring a Tudor arch with quarry-faced voussoirs and straight sides, flanked by battered buttresses. Above the arches and across the buttresses is a moulded ashlar stringcourse and blocking course, which serves as a cornice to finish the structure. Originally, both the central and south portals were designed for a single track railway, although the south portal's bore was excavated later, between 1868 and 1871, with its entrance built earlier in anticipation of the tunnel.

The north portal, designed for a double track, is taller and wider than the others. It features a Staffordshire blue brick horseshoe arch set within an ashlar roll moulding, flanked by two projecting quarry-faced buttresses or piers. Above the arch is an ashlar course, followed by a moulded and tooled string course and a tooled blocking course, which includes a large date stone at its center.