Roast Lamb with Potatoes

‘This is a dish which does not require much in the way of side dishes or other vegetables: it is a meal in itself. But a green vegetable such as broccoli wouldn’t go amiss. Even the cooking doesn’t involve much work, since the oven does it all. And it is also extremely economical because you can use cheaper cuts of lamb. My father always wanted the head of the lamb, cut in half, to be included in the roasting tray (the only one in the family to do so). What he particularly liked to eat was