If using the oven to cook your stew, preheat it to 180C/350F/gas 4. Trim the ends off your celery and roughly chop the sticks. Peel and roughly chop the onions. Peel the carrots, slice lengthways and roughly chop. Pick and roughly chop the rosemary leaves, discard the stalks.
Put a casserole pan on a medium heat. Put all the vegetables and rosemary leaves into the pan with 2 lugs of olive oil and fry for 10 minutes . Add your meat and flour.
Pour in red wine and tinned tomatoes. Give it a good stir, then season with a teaspoon of sea salt (less if using table salt) and a few grinds of pepper. Bring to the boil, put the lid on and either simmer slowly on a stove top or cook in an oven for 2 hours.
Remove the lid for the final half hour of simmering or cooking and add a splash of water if it looks a bit dry. When done, your meat should be tender and delicious. Remember to taste it before serving to see if it needs a bit more salt and pepper.