The island carries the name of a ship, the Lady Elliot, whose captain charted it in 1816. But its defining wound came later. From the mid-1800s, miners dug for guano, the phosphate-rich crust formed where centuries of seabird droppings had reacted with limestone, prized as fertiliser and, in that era, as a feedstock for explosives. The work was brutal and thorough. By the time it ended around 1873, the diggers had carried off not just the guano but roughly a metre of topsoil, and stripped the cay of nearly every tree. Photographs from the period show something close to a moonscape: a flat scab of coral rubble, treeless, baked, abandoned. The seabirds that had built the island's fertility over millennia were left a ruin where their forest had been.

Recovery did not come quickly, and it did not come by accident. A lighthouse had been built here in 1873, and it was the keepers and their successors who, from the 1960s, began the slow work of replanting, coaxing trees back into ground that had been carried off in sacks a century before. The grasses returned, then the casuarinas and the beachside palms, and with the canopy came the birds in their tens of thousands, white-capped noddies flocking through the branches until the island seems to breathe with them. Today the cay is a sanctuary run as a low-impact eco-resort, where nothing may be taken, not a shell, not a fragment of washed-up coral, and no fishing is allowed in its waters. The restoration is now part of the island's identity: proof that even a place mined to nothing can be made whole again.

Roll off the beach almost anywhere and the reef is right there, no boat required. The corals here are hard corals, more architecture than colour, and over and through them moves a crowded cast: the ever-present sergeant majors in their convict stripes, parrotfish crunching at the reef, butterflyfish, moon wrasse, the occasional triggerfish. Reef sharks patrol the edges, timid and harmless. But the animals people fly here for are the big graceful ones, the manta rays that gather to feed and to be cleaned, and the turtles. Green and hawksbill turtles cruise the shallows year-round, unbothered by snorkellers, often curious enough to drift alongside, and in summer they haul up the beaches at night to lay. The reef asks only a little caution, reef shoes against the camouflaged stonefish, hands kept off anything cone-shaped, for the few residents that bite back.

Every place this remote keeps its sadnesses, and Lady Elliot keeps the story of Susannah McKee, wife of a lighthouse keeper, who in April 1907 walked out onto the old guano jetty in her best clothes and into the sea. The isolation, the accounts say, had become more than she could carry. It is a quiet, human counterweight to the brochure version of paradise, a reminder that for the people who once tended the light, this dot of coral in a vast ocean could be a kind of imprisonment as much as a refuge. The resort bar mixes a cocktail in her memory, an odd small tribute, but the island does not pretend its beauty was ever uncomplicated for those who lived alone on it, watching the same horizon close around them night after night.