Pumpkin stew

Name: Pumpkin stew
Ingredients: 2 tbsp vegetable oil; 500g stewing beef, cut into chunks; 2 onions, sliced or chopped; 600g carrots, cut into chunks; 1 celery stick, roughly sliced; ¼ small bunch of thyme; 2 bay leaves; 1 ½ tbsp tomato purée; 1 ½ tbsp plain flour; 1 l vegetable stock; 250ml ale or beer; 1 medium pumpkin (about 500g), peeled, deseeded and chopped; mashed potato or crusty bread, to serve