North of the Tristan archipelago, the weather and sea state underwent a dramatic change, as though we had sailed through a door into another world. We have left behind the Furious Fifties and the Roaring Forties, crossed the subtropical front – the great boundary of currents that forms the southern margin of the South Atlantic Gyre – and entered one of the world’s great latitudinal zones of high pressure, a region of sunshine and light winds. The sea is deep blue, and we’re wearing t-shirts. The geography of the ocean is all around us as we make our way slowly north on this planetary scale voyage.