Preheat the oven to 200°C, 400°F, Gas Mark 6. Cook the bacon rashers under a hot grill, turning once during cooking until golden. Remove from the heat and chop.
Add the flours, salt, bicarbonate of soda, bacon, sage and celery to the bowl, fit dough hook and blend on speed 2 for 1 minute, until combined. Add the yoghurt and milk and blend on speed 1 for 2 minutes, until a soft dough forms.
Turn the dough out onto a lightly floured surface and roll into a ball. Place on the baking sheet and flatten slightly. Using a sharp knife score a cross in the top. Sprinkle the top with flour and bake for 35-40 minutes, until golden. Serve with lashings of butter or good cheeses.