History in Structure

Britannia Bridge

A Grade II Listed Building in Porthmadog, Gwynedd

More Photos »
Approximate Location Map
Large Map »


Latitude: 52.9247 / 52°55'28"N

Longitude: -4.1275 / 4°7'38"W

OS Eastings: 257078

OS Northings: 338486

OS Grid: SH570384

Mapcode National: GBR 5P.MZTW

Mapcode Global: WH55L.KRR6

Plus Code: 9C4QWVFF+V2

Entry Name: Britannia Bridge

Listing Date: 26 September 2005

Last Amended: 26 September 2005

Grade: II

Source: Cadw

Source ID: 85367

ID on this website: 300085367

Location: At the N end of the harbour and standing between the town centre and the Cob.

County: Gwynedd

Town: Porthmadog

Community: Porthmadog

Community: Porthmadog

Built-Up Area: Porthmadog

Traditional County: Caernarfonshire

Tagged with: Road bridge

Find accommodation in


Built 1808-11 contemporary with the Great Embankment (The Cob), William Madocks' grand scheme to reclaim Traeth Mawr for agricultural land, and to carry a road on Madocks' proposed London-Dublin postal route. Construction was probably supervised by John Williams, agent to Madocks. The bridge acted as a tidal sluice, and retains its slots for tidal gates.


A double-carriageway 5-bay bridge, of large blocks of squared local stone laid in regular courses. The original construction is best observed on the N (landward) side. Segmental arches have freestone voussoirs, and keystones recessed. Prominent rounded cutwaters retain slots for tidal gates, and above them are shallow buttresses carried up to a raised band at the base of the parapet. The parapet spanning the river is C20, of coursed slate-stone. Above the abutments the original parapet has survived, which is lower, and curves out to round terminal piers, which on the E side abuts Bridge Cottage. On the S (harbour) side the bridge has been extended by widening of the deck to accommodate a footway, which is supported on the cutwaters. These cutwaters also retain slots for tidal gates. The C20 parapet is similar to the parapet on the N side.

Reasons for Listing

Listed, notwithstanding later widening, as an integral component of William Madocks' grand reclamation scheme, as represented by the Cob, and for its contribution to the historical integrity of the harbour. The bridge retains important evidence for its original design and construction.

External Links

External links are from the relevant listing authority and, where applicable, Wikidata. Wikidata IDs may be related buildings as well as this specific building. If you want to add or update a link, you will need to do so by editing the Wikidata entry.

Recommended Books

Other nearby listed buildings

  • II Bridge Cottage
    Set slightly back from the road immediately E of Britannia Bridge.
  • II The Sail Loft
    At the W end of Britannia Place and on the N side of Britannia Terrace.
  • II Plas Ynys Tywyn
    Set back from the road at its junction with High Street.
  • II Pioden (Magpie)
    In a terrace near the SE end of High Street, opposite Heol y Parc.
  • II Harbour Restaurant and house
    In a terrace near the SE end of High Street, opposite Heol y Parc.
  • II Former slate warehouse on Oakleys Wharf
    Forming the S end of Oakleys Wharf, at R angles to the quayside.
  • II Plas Ne Ne
    In the centre of a terrace of houses on the N side of Britannia Terrace (A487) and facing N.
  • II The Oakleys
    On Oakleys Wharf, set well back from the quayside and beyond the N end of the former slate warehouse.

BritishListedBuildings.co.uk is an independent online resource and is not associated with any government department. All government data published here is used under licence. Please do not contact BritishListedBuildings.co.uk for any queries related to any individual listed building, planning permission related to listed buildings or the listing process itself.

British Listed Buildings is a Good Stuff website.