The Norrard Rocks are not really islands in the usual sense. They are the surviving high points of a drowned plateau, what the sea has not yet finished taking. Gweal, the largest at just under six hectares, is really two hills lashed together by a boulder beach. Scilly Rock, a kilometre west of Bryher, has been split into two summits by a chasm so deep that local fishermen named them North Cuckoo and South Cuckoo. Mincarlo, the southernmost, hosts the largest cormorant colony in the entire archipelago. Maiden Bower is mostly bare; Seal Rock is barer still, with orache as its only recorded plant. A folklore tradition holds that Scilly Rock was the first piece of the original main island to split off, giving the whole archipelago its name.

European storm-petrels are smaller than starlings. They weigh about the same as a slice of bread. Yet they spend nearly their entire lives at sea, returning to land only to breed, and only in darkness, to colonies on islands free of rats and footprints. England has only one place where they breed: the Isles of Scilly, with eleven colonies and roughly 1,475 occupied burrows. Three of those colonies are here on the Norrards, on Mincarlo, Illiswilgig, and Castle Bryher, totalling just thirty-seven pairs. Castle Bryher alone holds seventeen of them, packed into a 0.39-hectare rock that rises 26 metres from the sea. Land here in daylight and you would crush nests you cannot see, scattered in crevices beneath your feet.

Human history on the Norrards is mostly the history of things going wrong nearby. In 1885, the ship Sussex foundered on Seal Rock; twenty-three of her cattle were salvaged from the wreck and landed on Gweal, where they grazed briefly before being taken off again. The arachnologist William Syer Bristowe came in 1928, 1929, and 1934, scrambling ashore in calm weather to record spiders no one else had bothered to look for. On Mincarlo he found six species, including Halorates reprobus, which lives in the dark warmth of cormorant and shag nests. The grey seals come ashore here to pup, hauling their bulk onto Illiswilgig and Seal Rock and Mincarlo each autumn. They are the only mammals that the Norrards belong to.

Most protected places allow some compromise. You can walk a marked trail. You can land at a designated spot. The Norrards offer no such concession. The Isles of Scilly Wildlife Trust manages them as nature reserves where the landing prohibition is absolute, year-round, and not subject to permits or exceptions. The reasoning is harsh and simple. Storm-petrels are precise. Cormorants are precise. The plants that cling here, the rock sea-spurrey and thrift and sea beet, are precise. Add disturbance and the system unravels. So the boats slow and the cameras click, and the islands remain themselves. Looking down from the air, the Norrards appear as scattered punctuation in a sentence written by the Atlantic, brief, hard, and pointedly uninterrupted.