The bleak, volcanic island of Ascension, 800 miles from its nearest neighbour St Helena, was described by a Victorian naval officer as 'one of the strangest places on the face of the earth'. It is still exceedingly odd. Uninhabited when it was taken over by the British in 1815, it was an almost perfect natural vacuum – a triangular heap of lava and ash. When the Royal Marines brought in plants and animals, some flourished, others died. Tropical forest now clothes the peak of Green Mountain, and feral donkeys haunt the plains. As sea birds swarm around the coast, radar stations monitor space from the tops of rust-red cinder cones, and primeval, giant green turtles lumber up the beaches to nest. The island's history is short but extraordinary.