Pour the just-boiled water into a heatproof measuring jug, add the stock cube, tomato purée and yeast extract. Stir well until the cube has dissolved and set aside.
Put the beef, bacon and vegetables in a slow cooker, sprinkle over the flour and add the salt, herbs and plenty of freshly ground black pepper. Toss together. Add the stock mixture and stir well.
Cover with the lid and cook on low for 8–10 hours, until the beef and vegetables are tender. Serve with mashed potatoes.