Preheat the oven to 250°C / 475°F / Gas 9. Season joint with salt and pepper just before cooking. Sear the meat for 15 minutes in the oven.
Reduce temperature to 180°C / 360°F / Gas 4 and cook for 25 – 30 minutes per 450g (lb). Once joint is cooked, rest it in the warm place for at least 20 minutes.