Heat a casserole pan until really hot and add about a tbsp of oil. Fry the lamb until browned all over. Make sure and get some good colour on the meat at this stage as it will enhance the flavour of the finished dish. Remove the lamb from the pan with a slotted spoon and set aside.
Reduce the heat and add the knob of butter to the pan. Fry the onion, celery and carrot for a few minutes, scraping any bits of lamb from the bottom of the pan.. Cover and leave to ‘sweat’ for 10 minutes, stirring occasionally.
Add the garlic and rosemary and return the browned meat to the pan. Sprinkle over the flour and stir everything together. Turn the heat up and add the wine. Stir and allow to bubble over a fairly high heat for 5 minutes or so, until the wine has reduced slightly. Add the stock and season. Bring to the boil, cover, reduce heat and leave to simmer gently for 1 and a half hours, checking and stirring occasionally.
Serve with Special Potatoes and lots of lovely vegetables.