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Cof Cymru: National Historic Assets of Wales · Wales

Tunnel Passage at Fort Williamsburg

Llandwrog, Gwynedd, Wales

The record

Designation
Listed building, Grade II*
Broad class
Defence
Date of designation
29 May 1968
Locality
Glynllifon
Community
Llandwrog
Unitary authority
Gwynedd
Country
Wales
Coordinates
53.07087, -4.29978
Cadw reference
20466

Slide toward Today to fade the historical sheet and see the modern map underneath.

David Rumsey Map Collection, Stanford Libraries

Shown on 5 historical map sheets, the earliest the 1795 "To Sir Watkin Williams-Wynn Bart ... the map of the six counties of North Wales is most humbly inscribed by his obedient humble servant" (Llyfrgell Genedlaethol Cymru – The National Library of Wales).

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This record in Cadw's own full report ↗

Cadw's description

On the northern side of the Fort linking the former Parade Ground and the Tower and beyond to the outer bastions. Fort Williamsburg is approximately 0.5km south-east of the house.

Fort Williamsburg was built by Sir Thomas John Wynn in 1761 following his election as MP for Caernarvonshire and his appointment as Constable of Caernarvon Castle and Lord Lieutenant making him responsible for the county's militia. He was a notable eccentric of his day and he carried out these responsibilities in an unparalleled way, by building his own private garrison within the park at the family home.

On the day of George III's coronation (September 1761) Wynn founded 'The Society or Garrison at Fort Williamsburg in Glynllifon Park' and he also created 'The Holy Order of Sisterhood United, Connected and Regulated with the Free, Firm and Friendly Garrison of Williamsburg' - a unique volunteer organisation. The intention was for the garrison to comprise a Commander in Chief, a Governor, Lieutenant-Governor, 100 Officers, an Archdeacon, 24 chaplains, 24 honorary members and an unlimited number of volunteers. Although the officers were not part of the regular army they wore full and colourful uniform all at Wynn's expense.

The Caernarvonshire Militia was mobilised for a year while there was a threat of French invasion but even after the 1763 Treaty of Paris the muster books show that the Williamsburg garrison continued to meet. However, having realised that Fort Williamsburg had limited strategic capability, and with the American War of Independence once again threatening British shores, Wynn began work on Fort Belan begun in 1775.

The tower is said to be a later addition and if so this tunnel passage is likely to be contemporary with that as its primary function is to provide access to the tower.

Tunnelled through the 'defensive' mound bordering the parade ground. Stone walled passage descending all the way from the tower and turning into the tunnel beneath a brick arched opening. Within the tunnel the sides are cement rendered and the pavement has brick tracks.

The fort is roughly square with redans to the four corners and with surrounding ditches and revetment walls.

Listed grade II* as an integral part of this rare and remarkable British example of an C18 private fortification.

Group value with other listed items at Fort Williamsburg.

Nearby in the register

Other entries of the same register within about three miles of this one, by straight line.

Designated Historic Asset GIS Data, The Welsh Historic Environment Service (Cadw), 2026-09-07, licensed under the Open Government Licence http://www.nationalarchives.gov.uk/doc/open-government-licence/version/3/ Cadw, the Welsh Historic Environment Service · Open Government Licence v3.0
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