Qualla: Nant Ffrancon Pass

Nant Ffrancon Pass: Introduction

Mon, 25 May 2026 00:00:00 GMT

Photo credit Lines, R., fl. ca. 1840 Day & Haghe (Firm), Public domain. Geography teachers love Nant Ffrancon. It is the kind of glacial valley that turns up in every undergraduate textbook chapter on the work of ice: the broad U-shaped cross-section, the truncated spurs along its sides, the hanging valley of Cwm Idwal spilling its meltwater off the southern wall in the Ogwen Falls. Most U-shaped valleys in Britain are middling examples or compromised by farmland. Nant Ffrancon is the real thing. From the air, dropping in toward the A5 from the east, you see the floor of the valley laid flat between two great mountain walls - the Glyderau to the south, the Carneddau to the north - and the road following exactly where ice once flowed.

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Image: Lines, R., fl. ca. 1840 Day & Haghe (Firm) | Public domain

Nant Ffrancon Pass: What the Ice Did

Mon, 25 May 2026 00:00:00 GMT

Photo credit Williams, H. W. (Hugh William), 1773-1829 Woolnoth, William, fl. 1785-1836, engraver., Public domain. About 18,000 years ago, the last great ice sheet flowed down what we now call Nant Ffrancon, gouging a deep trough between the rising Glyderau and Carneddau ranges. As it moved, it widened the original V-shaped river valley into a U; truncated the lower ends of side ridges into t...

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Image: Williams, H. W. (Hugh William), 1773-1829 Woolnoth, William, fl. 1785-1836, engraver. | Public domain

Nant Ffrancon Pass: Lord Penrhyn's Road

Mon, 25 May 2026 00:00:00 GMT

Photo credit Jeff Buck, CC BY-SA 2.0. Until the late eighteenth century, getting through Nant Ffrancon was awkward. The valley floor was boggy; the only routes were rough tracks for drovers and pack horses. Richard Pennant, 1st Baron Penrhyn - the local slate baron, owner of the great Penrhyn Quarry on the northern s...

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Image: Jeff Buck | CC BY-SA 2.0

Nant Ffrancon Pass: Thomas Telford and the Mail Coaches

Mon, 25 May 2026 00:00:00 GMT

Photo credit Mat Fascione, CC BY-SA 2.0. Between 1810 and 1826, Thomas Telford re-engineered the route through Nant Ffrancon as part of the London-to-Holyhead trunk road - now the A5. The brief was political: faster, safer mail coaches between London and the Irish-bound ferries at Holyhead, after the Acts of Union folde...

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Image: Mat Fascione | CC BY-SA 2.0

Nant Ffrancon Pass: The Khyber Pass and the Himalayas

Mon, 25 May 2026 00:00:00 GMT

Photo credit Geoff Charles, CC BY-SA 4.0. The valley's dramatic, treeless, almost lunar profile has made it a recurring stand-in for other places in British cinema. The 1968 Carry On film Carry On up the Khyber used Nant Ffrancon as the Khyber Pass between India and Afghanistan - and the joke that the British army made a...

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Image: Geoff Charles | CC BY-SA 4.0

Nant Ffrancon Pass: From the Air

Mon, 25 May 2026 00:00:00 GMT

Photo credit Voice of Clam, Public domain. From the air, dropping in west of Capel Curig in summer evening light, the textbook qualities of the valley are unmistakable. The flat floor where ice once flowed. The smooth U-shaped walls climbing on either side. The hanging cwm of Idwal cut into the southern wall with the dark...

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Image: Voice of Clam | Public domain