Pierce the lamb all over using a sharp knife. Drizzle over the oil, then sprinkle over the spices, a good pinch of salt and black pepper, and the Worcestershire sauce. Massage the shoulder well until the marinade becomes a paste and chill for at least 1 hr or overnight in the fridge.

Prepare the barbecue – you will need a low temperature, around 125-140C with ashen coals (I put some lit coals onto unlit coals, and a fist-sized chunk or two of seasoned cherrywood to flavour the lamb. If using a gas barbecue, see tip.) Cook the lamb for 2-3 hrs (it will be cooked at this point), then transfer to a flameproof roasting tin. Peel the garlic and add to the tin with the red pepper, onions, chillies, vinegar and stock. Cook for another 1-2 hrs until the lamb is 92C when a temperature probe is inserted, or the shoulder blade slides out easily.

While the lamb is cooking, prepare the salsa. Put the chillies, peppers, onions and tomatoes directly into the embers, or on the gas barbecue flame. Remove each ingredient once blistered. The chillies will only need 30 seconds or so, but the onions will need at least 15 mins. Roast the garlic bulb to the side of the embers or flame until soft. Leave everything to cool, then squeeze the onions and garlic out of their skins. (Keep the charred skin on everything else.) Chop all the veg, discarding the stems and seeds, then put in a bowl. Drizzle over the olive oil and pour in the vinegar to taste. Add a good pinch of salt and black pepper, then stir in the mint.

For the sumac shallots, put the shallots in a bowl, then sprinkle over the sumac, sugar and a pinch of salt. Drizzle in the olive oil and the red wine vinegar, and mix well.

Once the lamb is cooked, remove from the tin, pull out the shoulder blade and put the meat on a platter. Tip the veg and juices from the tin into a food processor, or use a hand blender to blitz everything together and create a chilli sauce. Serve with the flatbreads and the chopped parsley sprinkled over.