Preheat the oven to 130C, Gas Mark 1
Chop 2 garlic cloves into slivers, cut slits in the leg of lamb and insert the garlic and rosemary.
Add olive oil to a pan and gently sear the lamb on both sides.
Add some olive oil to the roasting tin and place the lamb into it.
Chop the onion and garlic and add to a pan, sauté until soft.
Chop the chorizo and add to the pan, cooking gently for a minute
Pour in the wine and stock and add the tomatoes. Bring to a boil and simmer for a minute.
Pour over the lamb and cover the roasting tin.
Cook for three to four hours until tender.