A handy recipe to have in your repertoire. Mix the psyllium powder with 300ml/10fl oz water. Set aside to allow the mixture to thicken. Tip the flour and nigella seeds into a mixing bowl.

Add the remaining tomato sauce ingredients and 100ml/3½fl oz water, stir well to combine. Season with salt and pepper. Bring to the boil, then simmer for 18-20 minutes, stirring regularly, until ...