Heat a fry pan with butter and oil and sear the lamb joint all over until browned. Remove and put aside.
In the same fry pan add more butter or oil if necessary and add the leek, onion and carrot. Cook, stirring often, until softened about 10 minutes.
Add the garlic and bacon. Cook for a few more minutes then add the tomatoes, red wine and stock. Add seasoning to taste (go easy on the salt as the stock is already salty).
Bring to the boil. Remove and add to the bottom of the slow cooker. Add the bay leaf and stir well. Place the lamb on top along with any meat juices.
Cover and cook for approx 6 1/2 hours. Turn the lamb over once half way through and stir the vegetable mixture.
90 minutes before serving, remove the lamb, add the beans and mix well. Return the lamb on top, cover and cook for a further 90 minutes.
When ready to serve, remove the lamb to a chopping board. Stir the vegetable mixture and divide between two deep plates or bowls (Pasta bowls are ideal). The meat will be very tender so no carving is necessary.
This is a rustic dish so you want to break the lamb into chunks and place on top of the vegetable mixture. Serve with warm buttered crusty bread.