1) Preheat oven to 220C/Gas 8.
2) In a large bowl whisk flours, baking powder, bicarbonate of soda, sugar, and salt. Cut in butter until mixture resembles coarse meal. Add buttermilk to dry ingredients, stirring until dry ingredients are moistened.
3) Turn dough out onto a lightly floured surface and knead lightly 4 to 5 times. Roll or pat dough out to about 2.5-cm thickness. Cut with a biscuit cutter and place on an ungreased baking tray. Bake for about 12 to 14 minutes or until brown. Serve warm.