In a small bowl mix together olive oil, red wine vinegar, sumac, paprika, cumin, coriander, garlic & seasoning. Place meat in a dish, pour over the marinade and massage it into the meat. Cover with cling film and place it in the fridge for 2-3 hours.
Remove lamb from the fridge, roughly chop bell pepper and thread meat onto the skewers alternating with chopped peppers. Grill on medium heat for 3-5 Minutes turning frequently.
Once cooked, squeeze over the lemon juice and serve with greek yogurt.
* Percent Daily Values are based on a 2,000 calorie diet. Your daily value may be higher or lower depending on your calorie needs.