Preheat oven to 190 degrees C. Lightly oil a baking tray.
Sift together the flour, sugar, baking soda, baking powder and salt. Mix butter into flour mixture using a pastry cutter or two butter knives, cutting butter into small pieces. Add buttermilk and mix to make soft dough. Stir in currants.
Knead dough on a lightly floured surface for 5 minutes, or until smooth. Form dough into a thick 18cm round and place on baking tray. Mark loaf into quarters with 1cm cuts from side to side and top to bottom. Bake for 40 minutes, until golden and crusty.