Preheat oven to 230c / 450F / Gas mark 8. Weight the crown roast and calculate roasting times.
Heat oil in the roasting pan and place the crown roast of lamb into the pan.
Place in the oven and cook for 20 minutes.
Now reduce the heat to 180c / 350f / Gas mark 4 and roast the lamb for 45 minutes per kilo or 16 minutes per pound. For the last half-hour of roasting add the rosemary sprigs between the bones and in the middle of the roast. If crown is stuffed allow an extra 25 minutes.
Turn off the oven and leave the meat to ‘rest’ whilst you make the gravy.
Serve with freshly steamed vegetables and roast potatoes with rosemary.
