1.Preheat the oven 220°C.
2.Place the lamb, onion, carrot and celery in a large roasting pan and season well with sea salt and freshly ground black pepper. Toss with olive oil and roast for 20 minutes, turning once, until the lamb and vegetables are lightly browned.
3.Reduce the oven to 160°C.
4.Remove the pan from the oven and drain off any fat. Add the wine, stock, tomato paste and vinegar. Scatter the garlic, rosemary and bay leaves over the meat and vegetables. Season with more salt and pepper and mix to combine. Cover the pan with foil, then roast for a further 2 hours or until the lamb is tender.
5.Increase the oven to 180°C.
6.Remove the lamb with tongs and place in an ovenproof serving dish. Strain the vegetables and cooking liquid through a colander into a large bowl, discarding the vegetables. Stand liquid for 5 minutes, then skim off any fat from the surface.
7.Pour liquid into a saucepan over high heat. Bring to the boil, then reduce heat to medium and simmer for 12-15 minutes or until reduced by one quarter.
8.Pour sauce over the meat, then return to the oven for a further 15-20 minutes, turning twice, until the sauce is well reduced and lightly coats the lamb. Sprinkle with parsley and serve.