Preheat the oven to 200°C (180°C fan).

Lightly dust a baking tray with flour.

Combine the plain flour, wholemeal flour, porridge oats, bicarbonate of soda and sea salt in a large bowl.

Add the butter and rub into the dry ingredients until evenly distributed.

Pour in the buttermilk and mix quickly using a table knife.

Bring the dough together gently with your fingertips, taking care not to overwork it.

Shape into a round loaf approximately 20 cm in diameter.

Transfer to the prepared baking tray.

Cut a deep cross into the top of the loaf.

Bake for 30–35 minutes until golden brown and the base sounds hollow when tapped.

If required, turn the loaf upside down and bake for a further 2–3 minutes.

Transfer to a wire rack and cover with a clean tea towel.

Allow to cool before slicing or breaking into wedges.