Take the lamb out of the fridge at least an hour before cooking. Pre-heat oven to 200 C.
Season the lamb with salt and pepper and put on a roasting tray. Place in the centre of the oven and then reduce the temperature to 180 C. Cook for 1 hour 15 minutes.
Remove from the oven. Transfer to a warm platter or tray, cover loosely with foil and rest for 20 minutes.
Carve thin slices across the grain (perpendicular to the bone) and serve accompanied with gravy and mint sauce and roasted vegetables.