Mix marinade ingredients, rub over lamb, then refrigerate at least overnight.
Remove lamb from fridge one hour before cooking. Preheat oven to 130°C.
Place lamb in a roasting dish with 200ml water. Cover with foil and cook for 2 1/2 – 3 hours. Reduce heat to 110°C and cook for another 1 1/2-2 hours. Add water if needed.
For the yoghurt: heat oil in a frying pan on a low heat. Add garlic and oregano and fry until garlic is golden, then add lemon juice to stop cooking process. Place mixture in a bowl with yoghurt and tahini and season to taste. Combine with a little water until it has a dolloping consistency.
For the pickling liquid: bring all the ingredients to the boil, then reduce to a simmer for 10 minutes.
Cut capsicum into bite-sized pieces. Cover with hot brine and allow to cool.
Cut cucumbers lengthways and slice into bite-sized chunks. Submerge in pickling liquid for at least one hour. Drain well.
Warm the flatbread in the oven.
Place capsicum, cucumber, pomegranate seeds, coriander, mint leaves and pieces of warm flatbread in a large mixing bowl. Dress with oil and vinegar and season.
Serve lamb warm from the oven (it will be tender enough to pull away using just a fork). Serve with tahini yoghurt and a salad.