Add diced beef,chopped onion and chopped red peppers to casserole dish..in a seperate plastic jug add two tins of tomatoes,tomato puree beef stock ,water,mustard and Worcestershire sauce..mix all up.pour the content's of the jug into casserole dish and mix together,add salt and pepper and slow cook in the oven for 4 hours,stiring occasionally,when ready serve with creamy mash potato