For the lamb, score the skin of the lamb lightly with a very sharp knife.
Mix together the salt, pepper, rosemary, sage and olive oil and rub the mixture into the lamb. Leave at room temperature to marinate for one hour.
Heat the oven to 230C/450F/Gas 8.
Heat the rapeseed oil in a large, heavy duty roasting tin over a medium heat on the hob. Add the lamb bones and meat trimmings and cook for 7-10 minutes, or until they are lightly browned all over. Do not colour the bones too much or the resulting jus will taste bitter and astringent.
Add the garlic to the pan, cook for about three minutes, or until lightly browned and then remove the pan from the heat.
Place the lamb shoulder on top of the bones and roast in the oven for 20 minutes. Sitting the meat on the bones allows the air to circulate so the meat cooks evenly. The bones will also provide extra flavour for the jus.
Meanwhile, boil the wine in a small saucepan for 30 seconds – this will remove the bitter alcohol content, soften any tannins in an oaked wine and bring out the depth and fruitiness of its flavour. Be careful not to over-boil or it will become flat and lifeless.
Remove the pan from the oven, baste the meat with the pan juices and strain off the excess fat.
Add the wine, 400ml/14fl oz water, bay leaf and thyme and stir to lift the caramelised juices from the bottom of the pan. This will create the jus and keep the meat moist as it cooks.
Turn the oven down to 150C/300F/Gas 2, cover the meat loosely with a piece of foil and return to the oven for four hours, basting with the juices every 30 minutes.
For the braised vegetables, heat the butter and oil in a large pan over a medium heat. Add the onions, carrots, Swiss chard stalks, lettuce and beetroot and a little sat and freshly ground black pepper. Cook for about five minutes, stirring gently from time to time, then add 50ml/2fl oz water.
Put the lid on the pan and cook the vegetables on the lowest heat for 35 minutes. This way of cooking allows the sugars in the vegetables to develop very slowly, giving a wonderful flavour and a soft, melting texture.
Add the Swiss chard leaves, replace the lid and cook on a high heat for a further three minutes, or until the chard has wilted. Stir gently, check the seasoning and keep warm until you are ready to serve.
When the meat is cooked, transfer onto a serving plate and rest in a warm place for at least 20 minutes before serving.
While the meat is resting, strain the juices from the roasting pan through a fine sieve into a small saucepan and pour off the excess fat that rises to the surface. Do not attempt to remove all the fat for it carries a huge amount of flavour from the roasting and gives a lovely silky texture to the jus. Season the jus to taste with salt and freshly ground black pepper, reheat gently and pour into a warmed sauce boat.
Now the fun starts! Place the lamb, vegetables and jus on the table for your guests to help themselves. The meat will be tender enough to carve with a spoon; the more orthodox way is to use a sharp knife.