Manod Quarry

Overview

A slate quarry east of Blaenau Ffestiniog, known formally as Bwlch y Slaters and also as New Manod, that secretly housed the National Gallery's entire collection -- including works by Rembrandt, Velazquez and Leonardo da Vinci -- through the Second World War.

History

Quarrying at the site began in the 1780s as open workings near the summit of Manod Mawr, with significant underground development following a tramway connection made in 1866; a second working opened in 1903. Following the fall of France in 1940, government surveyor Francis Rawlins inspected the quarry in September 1940 and identified five disused chambers suitable for secure, climate-stable art storage. Brick-built enclosures with environmental controls were built inside the caverns, and by summer 1941 the entire National Gallery collection had been moved there from Wales's earlier, more dispersed wartime storage sites; the paintings returned to London in 1945.

The names in this corner of the mountain repay care. This quarry is Bwlch y Slaters, also called Bwlch Manod or New Manod, at SH732455 — and it is not the Old Manod quarry at SH725452 half a mile to the west, which is the site that developed under the name Graig Ddu and has its own record here. Both have at times simply been called Manod. Both were also renamed Cwt y Bugail by a later owner, after a different quarry two miles away that had closed — a naming overlap already noted on MineArchive's own Cwt-y-Bugail Quarry record. The two are no longer wholly separable on the ground either: from the mid-1980s the untopping operation here worked over the summit and engulfed the derelict Graig Ddu, and what is quarried today is the combined site.

Geology

Slate east of Blaenau Ffestiniog; the vein is not named on the record.

Workings

Open workings near the summit of Manod Mawr from the 1780s, with significant underground development after the tramway connection of 1866. Brick-built enclosures with environmental controls were built inside the caverns in 1941.

Closure

Slate production was suspended in 1960 and resumed after 1985 with new milling equipment.

What remains

Managed as an active slate working in places and not open to the public; wartime infrastructure has mostly been removed, though the chambers used to store the paintings survive. The National Slate Museum at Llanberis holds an interpretive display on the site's wartime history, and the National Gallery itself unveiled an inscribed slate tablet in 2024-25 commemorating the quarry.

Related mines

• Cwt-y-Bugail Quarry — The two quarries share a genuine naming overlap -- the 'Cwt y Bugail' name used by a later owner belongs to a different, separate site.
• Graig Ddu Quarry — Neighbours on Manod Mawr, half a mile apart, whose names have been exchanged for two centuries: Graig Ddu opened as Manod Quarry and is the Old Manod of the sources, while Bwlch y Slaters is the New Manod, and a later owner renamed both together Cwt y Bugail. Since the mid-1980s the untopping operation at Bwlch y Slaters has worked over the summit and engulfed the derelict Graig Ddu, so the two are now physically one working.

Recorded claims

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

• Quarrying at the site began in the 1780s as open workings; significant underground development followed a tramway connection in 1866, and a second working opened in 1903. ¹
• Francis Rawlins surveyed the quarry in September 1940 and identified five disused chambers suitable for art storage; brick enclosures with environmental controls were built inside, and by summer 1941 the entire National Gallery collection, including works by Rembrandt, Velazquez and Leonardo da Vinci, was housed there until returning to London in 1945. ^1,2
• Production was suspended in 1960 and resumed after 1985 with new milling equipment. ¹
• Alfred McAlpine operated the quarry, by then locally known as Cwt y Bugail, until ceasing operations there in late 2007. ³

Photographs & further reading

Sources

1. (secondary) Bwlch y Slaters quarry — Wikipedia
2. (secondary) Manod Slate Quarry (Chwarel Manod) — Subterranea Britannica
3. (secondary) Bwlch y Slaters Quarry — Festipedia

Record created: 29 August 2026 · Last researched: 29 August 2026