Sift the flour and bicarbonate of soda into a large bowl. Add the salt and sultanas and stir to combine.
Pour in the buttermilk and mix until a soft and sticky dough forms.
Put the dough on a well-floured work surface and knead for a minute or two. Shape into a flattened ball and place on the prepared baking tray. Slit the bread and brush the loaf lightly with milk.
place on the base of the baking oven. Bake for 45–55 minutes, or until the underside sounds hollow when tapped. I always, while using the aga, halfway through to turn the bread to allow the front and the back of the bread to bake evenly.
once cooked, remove from the oven and transfer to a wire rack to cool.