Lay the butterflied lamb leg on a board and use a sharp knife to prick about 20 holes all over the skin side. Press the rosemary sprigs deep into the holes, then season all over.

To make the glaze, tip all of the ingredients into a small saucepan, reserving a few sliced chillies, and bring to the boil. Stir to combine, then remove from the heat and set aside. Light the barbecue. It’s ready when the coals are ashen and you can hold your hand 5cm above the grill for at least 5 seconds.

Lay the lamb skin-side down on the grill and cook for 10 mins. Turn over using tongs and cook for 10 mins more. Repeat this two more times for 5 mins on each side so the lamb cooks for a total of 30 mins. Baste with the glaze, turn the lamb again and keep basting for another 10 mins until deep brown and sticky. Remove to a board, cover loosely and leave to rest for 20 mins. Carve into thin slices to serve, then scatter over the reserved sliced chillies.