It is always easier to get your butcher to cut and clean the lamb for you, removing as much of the fat as he can. Ask him to make slashes in the meat for the marinade to seep into.
Ideally a 2kg leg of lamb would feed 8 to 10 people. Always plan to make more than you expect to use immediately –
leftovers can be used in wonderful sandwiches for lunch the next day.
If you are able, source oven-roasting bags. I’ve found that this retains the moisture during cooking, preventing the meat from drying out. Remove from the bag in the last 30 minutes to let the outside of the lamb crisp up and finally glaze.

INGREDIENTS
2kg leg of lamb
Water
1–2 tbsps vinegar
6–8 whole garlic cloves
MARINADE
2 tbsps ghee
3 tbsps white vinegar
3 tbsps red ginger and garlic masala
1 tsp ground ginger
1 tsp fine red chillies
1 tbsp ground cumin powder
1 tbsp ground coriander powder
1 tbsp salt
1 tbsp lemon pepper
½ cup butter
¼ cup lemon juice
½ cup fried onions, crushed
2 green chillies
1 tbsp black pepper
1 tsp sugar
SAUCE
1 tbsp tomato sauce
1 tbsp mayonnaise
1 tbsp Worcestershire sauce
1 tbsp Maggi chilli sauce
Prepare the marinade by mixing the marinade ingredients together in a pan. Add ghee, white vinegar, red ginger and garlic masala, ground ginger, fine red chillies, ground cumin powder, ground coriander powder, salt, lemon pepper, butter, lemon juice, fried onions, green chillies, black pepper and sugar. Allow this to simmer just long enough to combine all the ingredients.
Allow the mixture to become a thick paste. Smear it over the lamb, massaging well into the slits and any cavities. Place lamb with the marinating liquid into the oven-roasting bag and leave in the fridge overnight.
Remove from fridge and allow it to come to room temperature. Place into a large oven-proof tray and preheat the oven to 180°C.
Place the leg of lamb into the oven and drop the temperature to 140°C. Slow cook for 2.5 hours. Remove from the oven gently, remove the bag (be careful of the steam).
Spoon the juices over the leg of lamb and place baby onions, baby carrots and baby potatoes around the lamb (you can parboil these to ensure they are cooked to perfection with the lamb).
Mix together the tomato sauce, mayonnaise, Worcestershire sauce and Maggi chilli sauce. Spoon the sauce over the lamb.
Return the lamb to the oven and leave in for another 30 to 45 minutes, basting continuously. If you opt to leave the vegetables out, just add baby onions for the flavour.
I like to serve this with honey glazed carrots (prepared with salt, pepper, onion and butter) or crushed potatoes (boil the potatoes in salted water, remove and drain, crush with a fork. Sprinkle salt, black pepper, thyme and butter over the potatoes. Bake until the edges are crisp. Top with rosemary or thyme sprigs).