Pre-heat the oven to 160 degrees Celsius or gas mark 3 . After two, or more, hours of marinating, the lamb is ready to be cooked.
Transfer the lamb to a roasting dish and pop it in the oven to slowly and gently cook for 4 hours.
After four hours, take out the lamb and transfer to a plate, serving dish or chopping board to rest. Cover the meat in tin foil and leave to one side. Turn the oven up to 180 degrees or gas mark 4.
In the roasting tin you used for the lamb, you should be left with all of the juices and leftover marinade. This is what you're doing to roast your potatoes in. Add your chopped potatoes to the roasting tin and coat well. You don't need any further seasoning in there other than a sprinkling of cumin seeds, but these are optional.
Roast the potatoes for 45-50 minutes, turning regularly.
Serve the lamb with freshly chopped coriander and lightly toasted pine nuts. Add a side of warm flatbreads and pop into the middle of your table for a truly incredible feast.