For the mince, heat the oil in a large saucepan or flameproof casserole dish and cook the celery and carrots for 15 minutes, stirring occasionally until softened and lightly coloured. Add the beef and cook with the vegetables for a further five minutes until the mince begins to brown, stirring regularly to break up the meat.
Add the tomatoes, tomato purée, beef stock, sugar and bay leaf. Add a good pinch of salt and plenty of freshly 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 gluten free flour in a bowl and stir in the suet, salt and parsley, rosemary and thyme. 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. Lightly (gluten free) flour your hands and roll the mixture into 12 small balls.
Stir the mince well and remove from the heat. Drop the dumplings carefully on top of the mince then cover with a tightly fitting lid and return the pan to a medium heat. Cook for 18-20 minutes or until the dumplings are well risen.