Unfortunately it seems very hard to get your hands on mutton any more, which seems odd as not that long ago a mutton chop was fundamental in the British diet; almost no formal meal went by without it appearing somewhere. However, persistence and a good butcher should suffice.
Cover your borlotti beans with clean water and cook for 1½ hours. Check them, you want them cooked but not falling apart. Remove from the heat and drain, but keep the liquor.
Meanwhile season your mutton, get a frying pan hot, add a large knob of butter, and allow it to sizzle. Reduce the heat slightly and brown the leg of mutton in the pan. You want this to be a gentle buttery moment, not a ferocious burning moment.
Remove the mutton to an oven dish or deep roasting pan large enough to hold all the ingredients. Brown the bacon and bacon rind in the same frying pan then add to the mutton. Gently cook the vegetables and garlic (if the pan seems too dry add a bit more butter), and then add these to the mutton and bacon, and nestle the herb bundle in. Also add the cooked borlotti beans and bay leaves, season, and add the wine and stock. The contents of the dish, except the mutton, should be just covered; if this is not the case add some of the bean liquor.
Cover with tinfoil, place in a medium to gentle oven for 4 hours, turning the leg over every 40 minutes, and checking at about 3 hours with a knife. When it’s ready, check the seasoning, cut chunks of giving mutton from the bone, and serve in deep plates with beans, vegetables, bacon and juices.