Toss the lamb in flour that has been seasoned with salt and pepper; shake away excess and cook the lamb over high heat until browned all over; transfer to the bowl of a slow cooker.
Add remaining oil the the same pan and sauté onions, carrots and garlic, stirring, over a medium heat for about 2 minutes or until the onion is starting to soften and then add the tomato paste and cook stirring for a further minute.
Add the wine to the pan, bring to the boil and then stir in stock, undrained tomatoes, sugar and bouquet garni and bring the boil; pour over the lamb in the slow cooker, making sure the lamb is covered by the liquid.
Cover and cook for 6 to 8 hours on the low setting or until lamb is soft and fall off the bone (see notes).
Remove the lamb from the slow cooker and cover to keep warm.
Turn the cooker to the high setting, cook uncovered for about 30 minutes or until sauce thicken slightly, removing any fat from the surface.
Serve the lamb with the sauce, instant polenta and steamed green vegetables, if desired.
Suitable to freeze but not to microwave.
JULIE'S NOTES - I made this dish simultaneously in two types of slow cookers. It was interesting to see how the low settings differed between them. The cooking varied by about 2 hours, as one cooker had a much lower heat than the other. It is important to keep an eye out, taste as you go and use your own judgement. Bouquet garni is a bundle of fresh herbs, usually by leaf, sprig of thyme and parsley stalks, tied together with kitchen string. The bundle is removed at the end of cooking and discarded.