Combine the bulgur wheat, bread crumbs, oats, tinned tomatoes, onion, celery, carrot, green pepper, walnuts, soy sauce, mustard, thyme, sage and pepper in a very large bowl.
Use a non-stick loaf tin, 5x9 inches, and press the mixture into the loaf tin. Spread the optional ketchup over the top and bake for 60 minutes. If you've got a fan assisted oven keep an eye on it from about 40 minutes to ensure it doesn't burn.
Let it stand for 10 minutes before slicing and serving with your choice of veg.