1. Preheat oven to 425°F.
2. Make 8 to 10 small cuts in the lamb and insert garlic slices.
3. Rub olive oil all over the leg.
4. In a small bowl, mix together the thyme, rosemary, salt and pepper.
5. Transfer herb mixture to a large plate. Roll leg of lamb into the herb mixture until well-coated.
4. Place leg of lamb in roasting pan and roast for 20 minutes. Reduce heat to 350°F and roast for another hour or until a meat thermometer reads 130F (medium rare).
5. Allow to cool slightly before carving. Serve with new potatoes.