Preheat oven to 180°C, 350°F, Gas Mark 4. (170°C for fan assisted ovens)
Fry the lamb and onions with the oil in a pan until browned. Place in a casserole dish with the carrots and peas.
Mix the Colman's seasoning with water and add to the dish.
Top the dish with a layer of potatoes. Cover and cook in the oven for 2 hours.
Ensure piping hot and serve immediately with seasonal vegetables.