This is a proper old-school Sunday roast with crackling. Leaving the bone in adds a bit of extra flavour and having a layer of fat helps to keep the meat nice and moist as it roasts. This isn't the kind of joint you carve into neat slices. If you've cooked it right, it should pull apart into shreds with a couple of forks. If you're worried about scoring the crackling yourself, ask your butcher to do it for you, that's what he's there for.
This hearty lamb shoulder recipe, with its creamy mashed potato pairing, makes a wonderful and rustic lamb dinner. Slowly braising the lamb in a rich sauce, as Tom Aikens does here, ensures that the meat's full, immense flavour is drawn out.