Western promise

Twenty-eight miles west of Cornwall lies an untamed archipelago of footprint-free sands, crystalline waters and rare wildlife. And getting there is part of the adventure. Here's your guide to Scilly's inhabited islands

- Matt Baird

St Mary's

Eelgrass sways beneath my feet and beams of sunlight catch my goggles.

I’m swimming in my running shoes, but soon emerge onto the fine white sand and start to run in my wetsuit.

No, this isn’t some weird sporting dream but the annual St Mary’s Scilly Swimrun event: an amphibious 16km race around the perimeter of the archipelago’s biggest island, involving seven runs and seven swims - with stretches of scrambling, rock climbing, orienteering and snorkelling thrown in for good measure.

Home to most of the archipelago’s 2,366 inhabitants, pubs and ferry connections, the island of St Mary’s is an ideal base for a Scilly trip. The Swimrun route takes entrants through the islands’ largest settlement, bustling Hugh Town, and on to the 350-year-old walled fortification called the Garrison, where the 16th-century Star Castle (now a four-star hotel) lords over the headland and its cannons point west into the Atlantic Ocean.

The Isles of Scilly possess more archaeological sites per square mile than anywhere else in the UK - 238 of them, encompassing 900 individual protected and well-preserved features.

Prehistoric sites and Bronze Age burial chambers abound, especially on St Mary’s, along with relics from the civil, Napoleonic and world wars. The archipelago was also caught up in the Three Hundred and Thirty-Five Years’ War with the Netherlands from 1651. This was a conflict that really existed only as a technicality, with no casualties nor shots fired - a diplomatic oversight remedied in 1986 when a peace treaty was signed.

St Mary’s Swimrun continues around the headland and across the airfield, where I wait at traffic lights for a tiny plane to land. Further highlights include a sandy causeway at Pelistry Bay, the Innisidgen burial chambers and the mysterious Giant's Castle, a fort on an improbably rocky headland.