Roast Leg of Lamb Spiked with Rears and Rosemary

Generations of British cooks have ruined leg of lamb by overcooking it. It is a lean joint and if cooked until brown all through the meat loses both succulence and flavour. In France they often cook lamb leaving it almost red inside but I like it best a delicate pink. Lamb responds well when cooked with fruit; particularly, I have discovered, with pears. This is an easy dish to prepare and would do well for either Christmas Eve or Boxing Day. Sliced potatoes, cooked in a dish with garlic an