Cover the leg of lamb ½ the jar spice paste, cover and refrigerate for 24 hours.
Remove the lamb from the fridge and allow to come to room temperature.
Preheat oven to 180°C.
Heat a heavy based frying pan over a medium to high heat, add olive oil to the pan, when the oil is hot add the leg of lamb to the pan. Fry off the lamb in a little olive oil until its golden on all sides, then transfer to an ovenproof dish.
To the frying pan, add the onion, carrot and celery, add in the remaining curry paste, then add red wine. Reduce by half, then add tomatoes and stock. Season well with salt, pepper and sugar.
Pour the contents of the pan over the lamb, cover with foil and cook for 4hrs at 180 degrees, then remove the foil and cook for a further 30 mins.
Carefully remove the lamb from the dish and set aside to rest.
Blend the contents left in your dish for the most delicious curry gravy.
Serve with seasonal greens and creamy mash or rice.