Remove the lamb from the fridge half an hour before cooking. Place in a roasting dish fat side up and season. Bake in an oven preheated to 180C or 170C fan bake. The rules for doneness are 25-30 minutes per 500g for medium and 30-35 minutes per 500g if you like it well done.
Remove the steak from the fridge half an hour before cooking. Dry the meat before seasoning. Preheat a large frying pan (or BBQ) to a high heat. If using a frying pan, the heavier the base, the better heavy-based pans hold heat longer and cook the meat evenly. It's important not to overcrowd the pan or BBQ, or the meat will stew rather than sear. Cook the steak in batches or use two pans if need be. You should hear a big sizzle when the steak hits the pan – no sizzle means the pan isn't hot enough.
As a rule of thumb (for a steak 22mm thick) – cook 2 minutes each side for rare, 3-4 mins each side for medium-rare and 4-6 mins each side for medium. For well done, cook for 2-4 minutes each side, then turn the heat down and cook for another 4-6 minutes. Let the meat rest for a few minutes before serving. This allows the meat to absorb all its juice.