Thus the LSWR, and its engineer, William Galbraith, were left with a route from Exeter that would have to skirt around the north and west sides of Dartmoor.

Originally it carried a single track, but it was doubled in 1879 when a second viaduct of similar design was constructed next to it and the two were joined.

[a] Each truss was installed in about 2 hours 30 minutes, thus the work could be arranged around the railway timetable without closing the line.

The method, devised by engineer T. Wrightson and supervised on site by W. Jacomb, worked well, and the entire ironwork was erected in 16 weeks.

It has a slight curve[b] which, combined with its exposed position, resulted in speed and weight restrictions being applied to trains crossing it.

In 1944, to allow heavy wartime traffic, the outer trestle legs were weighted with additional concrete to resist uplift.

In 1970, a road was built across the viaduct to permit lorries access to the Meldon Dam construction site.

[6] The bottom (tension) members of each newer truss include a continuous plate underneath for extra strength.

Each column is made of a varying number of sections, end-to-end, each consisting of six flanged curved pieces riveted together side-by-side.