Preheat the oven to 180C/350F/Gas4.
Heat the oil in a very large ovenproof saucepan then add the onion, garlic, celery and carrots and cook gently for 15 minutes, stirring occasionally, until the vegetables are beginning to soften and lightly colour. Add the beef and cook with the vegetables for a further five minutes until the mince is no longer pink.
Add the tomatoes, tomato purée, beef stock, sugar and bay leaves. Add four teaspoons of salt and plenty of ground black pepper. Bring to the boil, then reduce the heat and simmer gently for 20 minutes, stirring occasionally.
To make the dumplings, put the flour in a bowl and stir in the suet, salt and parsley, thyme and rosemary and mix until well combined. Make a well in the centre and add enough cold water - you’ll need around 200ml/7fl oz - to mix to a soft, spongy dough. Remove the dough from the bowl and use lightly floured hands to roll into 12 small balls.
Remove the mince from the heat and drop the dumplings carefully on the top, cover with a tight-fitting lid or aluminium foil and place in the oven for 18-20 minutes or until the dumplings are well risen and light.