An explorer's guide to the islands of Britain

51.377620, -3.120921
Distance: 2.1 km
Difficulty: 2/5
Method: Walking
Wow Factor: 7 out of 10

Key Facts

  • Location: Bristol Channel, south of Cardiff, Wales
  • Size: 35 hectares
  • Terrain: Easy grass paths; some free-range walking
  • Access: Boatrip from Cardiff
  • Height gain: 44 metres
  • Map: OS Explorer 153
  • Starting point: Mermaid Quay, Cardiff Bay. Lat/Long 51.463040, -3.164097; GR ST 192 744
  • Accommodation/food:

    Drinks, limited selection of snacks, and toilets at the island’s Gull and Leek pub. Dormitory accommodation in the farmhouse, camping and self-catering at Fog Horn Cottage can be booked through Cardiff harbour Authority at

  • Island Summary:

    Flat Holm is a limestone island lying in the treacherous currents of the Bristol Channel, approximately four kilometres off the coast of Wales. Its gentle grassy slope rises from the exposed rocky shore of the west to the more sheltered easterly cliffs. The interior is open, flat, and windswept. Managed by Cardiff Council it is a significant nature reserve. Yet it is not only natural forces that have shaped the island’s character. Augustinian monks, a radio genius, Victorian gunners, and cholera sufferers have occupied it over the last 800 years and all made their mark.

  • Look out for:
    • Large gull colonies
    • Explore a trove of military history
    • Great views to Wales, Somerset and Devon
    • Gull and Leek pub
  • Route description:

    A clockwise route from the Barracks building takes in the stunning panoramas of the Bristol Channel, historic military buildings and wildlife.

  • Getting there:

    By RIB operated by two companies from Mermaid Quay CF10 5BZ. Bay Island Voyages run daily 2–2.5 hour excursions and Cardiff Sea Safari run a more limited service on specific dates that allows 10–12 hours on the island

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