Nent Force Level

Overview

A four-mile drainage level driven under Alston Moor to dewater the Nent Valley's lead mines, designed by the engineer John Smeaton and built, in fits and starts, over 66 years. It never achieved its goal of finding new ore, and became known instead as a Victorian tourist attraction, offering underground boat trips through some of the largest man-made passages in the northern Pennine orefield.

History

Nent Force Level was designed by the civil engineer John Smeaton, already famous for the Eddystone Lighthouse, and driven from an entrance near Alston under the course of the River Nent toward Nenthead. Construction began on 10 June 1776, funded by the Commissioners of Greenwich Hospital — who administered the mineral rights of the Greenwich Hospital estate on Alston Moor — at a cost that eventually reached around £80,000. The level's dual purpose was to drain the lead mines of the Nent valley to allow deeper working, and to explore for new mineral veins along its course. Progress was slow and intermittent. Though initially designed at nine feet in height and width, the level was driven much larger in many stretches, expanding to between sixteen and twenty feet, and extended some three and a quarter miles from its Alston portal to Nentsbury engine shaft. Funding repeatedly ran out before the level reached Nenthead as intended, and construction dragged on for decades; the level is usually described as substantially complete by around 1810, with further work continuing into the 1840s. Contemporary observers were struck by its scale: the mining writer Westgarth Forster (1821) and the engineer Thomas Sopwith (1833) both described it as a 'great' or 'stupendous aqueduct'. Commercially, the level was judged a disappointment: it found no significant new mineral veins along its course, and by 1890 it was being called a 'total failure' as a prospecting tool, earning the nickname 'Smeaton's Folly'. Its drainage function was later superseded by hydraulic pumps. What it did become, through the first half of the 19th century, was a genuine visitor attraction: local inns arranged underground boat trips in thirty-foot boats, propelled by wooden projections from their sides, so that daytrippers could be rowed through the passages to view the geological formations and mineral veins exposed along the way. The mining company retained the tourist boats until around 1900.

Workings

A single long drainage level driven roughly three and a quarter miles from its Alston portal to Nentsbury engine shaft, mostly excavated well beyond its original nine-by-nine-foot design, reaching sixteen to twenty feet in height and width along much of its course — among the largest man-made underground passages in the northern Pennine orefield.

What remains

The original Alston portal was destroyed by later quarrying on the site; the level has since been reopened via a new entrance on private land and is accessible only to mine researchers with specialist equipment, via intermediate points such as Brewery Shaft. There have been periodic proposals to develop a heritage centre to make the level accessible to the public again, but it remains, for now, extremely difficult to visit.

Abandoned workings can be dangerous — unstable ground, uncapped shafts, flooding and bad air are common even where a site looks safe from the surface. This entry describes history and general location only; it is not an access guide.

Recorded claims

Individual factual claims, each attached to the source(s) that support it below. Where sources disagree, both are kept.

• Construction of Nent Force Level began on 10 June 1776 to a design by the engineer John Smeaton, funded by the Commissioners of Greenwich Hospital at a cost of around £80,000. ¹
• Though designed at nine feet by nine feet, the level was driven much larger along many stretches, expanding to between sixteen and twenty feet in height and width. ¹
• The level runs about three and a quarter miles from its Alston entrance to Nentsbury engine shaft. ¹
• By 1890 the level was being described as a 'total failure' for its goal of finding new mineral veins, and it became known as 'Smeaton's Folly'. ¹
• During the first half of the 19th century the level was a tourist attraction, with visitors rowed through the passages in thirty-foot boats propelled by wooden projections; the mining company retained the boats until around 1900. ¹
• The original Alston portal was destroyed by later quarrying; the level is now accessed via a new entrance on private land. ²

Sources

1. (secondary) Mysteries of the Nent Force Level — Salvin House (Alston Moor local history)
2. (secondary) Old Cumbria Gazetteer: Nent Force Level Portal, Alston — Old Cumbria Gazetteer

Record created: 26 August 2026 · Last researched: 26 August 2026