Marinated, Butterflied Leg of Lamb with Garlic Potatoes

This is one of my most regular regulars. It is the flattened, boned leg which, opened up, makes a vaguely butterfly shape. In summer I cook it on the grill in the garden. This year I started doing it in winter, as well, in a gas mark 7/210°C oven for about 45 minutes and it was wonderful. Winter lamb may not be as tender as it is in spring and summer, but the taste is deeper and better, really, and the marinade sees off any potential toughness, despite the unforgiving heat of the oven. I do