Mix dry ingredients, mix in water. Rise 2 – 3 hrs. or until doubled.
Preheat the oven to 240°C/450°F (220°C fan). Half an hour before the dough is ready, put a 24-28cm heavy based pot/Dutch oven with a lid in the oven to preheat.
Tip the dough onto a clean working surface, that's been lightly dusted with flour. Reserve 1/3 cheese for the topping. Sprinkle 1 tbsp flour on top of the dough and lightly flatten. Spread 1/2 of the marmite, followed by 1/3 of the cheese. Fold and repeat. Flip onto a 30cmx 30cm square piece of baking paper with the seam at the bottom. Pile the reserved cheese on top.
Remove hot pot from the oven. Use paper to transfer dough into the pot, keeping it on the paper. Put lid on. Bake 35 minutes. Remove lid. Bake 10 minutes to colour the surface. Remove pot from oven. Use paper to transfer bread onto a cooling rack. Remove paper. Cool at least 10 minutes before slicing.