1. Make sure the meat is at room temperature and not ice cold. Preheat the oven. Make 12 small incisions all over the leg of lamb with the tip of a sharp knife. Press a piece of garlic, a strip of anchovy and a few rosemary leaves into each hole. Rub the meat with the olive oil and season generously with salt and pepper.
2. Place the onion, carrot, celery and herbs in the bottom of a large roasting pan and add the water. Place the lamb directly on the oven shelf with the roasting pan of vegetables on the shelf below to catch the fat while the lamb roasts. In this way, the heat can circulate right around the meat. This method also works well in a kettle braai if you prefer to cook outdoors.
Once the meat and vegetables are in the oven, reduce the heat to 180°C. Roast the meat for 1 hour and 10 minutes until it is blush-pink inside, and slightly more done on the outside – the combination of blush-pink and more well done slices should satisfy (almost) everyone at the table! Let the meat rest well before carving.