Method

1. Preheat the oven to 240°C. In a pestle and mortar, pound the garlic, half the oregano, lemon zest and a pinch of salt. Then add the lemon juice and a drizzle of olive oil.
2. With a sharp knife, pierce the lamb all over, then push as much of the herb paste as possible into the holes.
3. Tip the potatoes in a large roasting tin, then toss in the remaining olive oil and remaining herb paste. Nestle the lamb among the potatoes. Place the tray in the oven and roast for 20 minutes, then reduce the temperature to 180°C.
4. Roast for a further 1 hour 15 minutes for medium rare (add an extra 15 minutes for medium). Baste the lamb once or twice with the juices and toss the potatoes during this time.
5. When the lamb is done to your liking, remove from the tray and allow to rest.
6. Remove the potatoes from the tray, sprinkle the remaining oregano onto them and keep them warm.
7. Place the roasting tray over a medium flame, add the canned tomatoes and olives to the pan juices and then simmer for a few minutes to create a sauce.
8. Serve the lamb with potatoes and sauce and a Greek salad on the side.