Preheat the oven to 160°C/320°F/gas 3. In a nonstick frying pan, fry the lamb - as much as you can fit in a single layer - until brown on both sides, in 1 tablespoon of vegetable oil. Remove to a plate and repeat with the rest. When all the lamb has been browned, transfer to a large casserole dish.
Add the remaining oil to the pan and fry the onions until soft and golden. Add the garlic and peppers, then cook for another 4 mins.
Stir in the curry powder and cook for a minute, then add the tomatoes - breaking them up with a wooden spoon - and creamed coconut. Stir to combine, then add to the lamb. Season, cover and cook in the oven for 2 1/2 hrs. Stir in the coriander and serve with boiled long grain rice.