Step on to Tenby’s Castle Beach at high tide and St Catherine’s Island is tantalisingly close, yet inaccessible. However, at low tide, weather permitting, this marvel of the Welsh coast is waiting to be explored, thanks to a band of volunteers.


St Catherine’s is a dramatic limestone outcrop, 200m long, 60m wide and 28m high. Conquering it means climbing 74 steps to reach a 10m steel bridge spanning the final moat-like ditch defence.

Fort on an island
St Catherine's Island and Fort with Caldey Island in the distance/Credit: Simon Whaley

History of St Catherine's Island

Solitude-seeking 12th-century visitors founded a small chapel here dedicated to St Catherine, but today, it’s the substantial shell of a Palmerston Fort that crowns this incredible islet.

The fort was built in 1867 to protect the naval dockyard at Pembroke and Milford Haven’s deep-water anchorage from a perceived Napoleonic threat, but thankfully it was never needed. Its imposing, black metal doors give it a prison-like atmosphere. Fans of the BBC series Sherlock may recognise the location from the 2016 episode, ‘The Final Problem’, when it doubled as a North Sea prison.

Vast windows overlooking Pembrokeshire’s glorious coastline now fill the gaps once taken by Napoleon-deterring seven- and nine-inch artillery.

Fort on an island
Interior of St Catherine's Fort/Credit: Simon Whaley

The 20th century saw many new guises for the fort. In 1907, the Windsor-Richards family turned it into a luxury home. Step along its central corridor, and it’s easy to imagine the gun casemates on either side making cosy rooms with captivating sea views.

Garrisoned during the First World War, and compulsorily purchased by the government at the outbreak of the Second World War, little remains of its residential history because Harrods auctioned off most of the internal fittings in 1940.

St Catherine's Island zoo

Between 1968 and 1979, the fort housed a zoo with over 100 animals, including monkeys and an alligator. Occasionally, the monkeys escaped and stole from tourists on the beach below. It’s still a haven for wildlife, with the area below the high waterline designated a SSSI, and the cliffs home to choughs and peregrine falcons.

Seaside town
Enjoy a spectacular coastal walk from Saundersfoot to Tenby/Credit: Getty

Visiting St Catherine's Island

For a magical experience, set off from Saundersfoot on a 4.5-mile stroll along the Pembrokeshire Coast Path, culminating at St Catherine’s Fort in Tenby. Take the bus or train back to the start.


Simon Whaley
Simon WhaleyAuthor, writer and photographer

Simon Whaley is a Shropshire-based author, writer, and photographer.