How long do you cook a 1.1kg leg of lamb for?

The general rule for lamb is, for every kilogram of weight, cook for an hour at 190 - 200 degrees Celsius, depending on the efficiency of your oven, or 180 degrees for a fan-forced oven. Thus, a 1.1 kg leg of lamb will take an hour and about ten minutes. It is advisable to use a meat thermometer to check at about half an hour before the expected time of finishing