Sift together flour, sugar, salt, and bicarbonate of soda in a large mixing bowl.

Make a well in the center and pour in most of the buttermilk.

Stir until a raggy, soft dough forms.

Add more buttermilk sparingly if needed.

Blend quickly until the dough has a floury, raggy consistency.

Turn the dough out onto a lightly floured surface and knead for about 30 seconds.

Shape the dough into a slightly domed circle about 6 to 8 inches in diameter.

Place the dough on a lightly floured baking sheet.

Use a sharp knife to cut a cross about halfway down through the sides of the circle.

Bake for 10 minutes in a preheated oven at 350-400°F (175-200°C).

Decrease the heat and continue to bake for another 30-35 minutes, until a hollow sound is produced when tapped.

For a crunchy crust, place the cooked loaf on a rack to cool.

For a softer crust, wrap the loaf in a clean dishcloth as soon as it's out of the oven.

Slice or split and serve warm with butter and jam.