Pre-heat barbeque to a high heat (hood down).Remove lamb from the fridge 30 minutes before cooking.Place oil in a bowl, add rosemary brush.Brush oil all over lamb and season.
Reduce heat to medium.Place lamb on hot grill plate, skin side down.Cook for 15-20 minutes on each side, hood down or until an internal doneness of 58◦C.Drizzle with lemon juice.Transfer lamb to a chopping board, cover loosely with foil and rest for 15 minutes.
Slice the lamb across the grain and serve with chargrilled lemon, cauliflower, tahini yoghurt and Lemon and Tomato salad.