Place joint in a bowl, marinate in brown ale, cover and refrigerate for 24 hours (or overnight). Drain and reserve the ale, then pat meat dry.
Preheat oven to 160°C/Fan 140°C/Gas 3. Heat oil in casserole pan, brown meat and transfer to a plate.
Sauté shallots and garlic until softened, add bay leaf, sugar, Worcestershire sauce, tomato paste, and seasoning.
Deglaze pan with the reserved ale, return meat to pan and bring slowly back to a boil. Cover, cook in oven for 45 minutes, then add veg and 'stock pot'. Baste the brisket (add a little water if required) and re-cover. Return to oven for 2 - 2 1/4 hours until a fork slides easily in and out of the meat.
Remove meat from pan, cover with foil and rest. Add cornflour to sauce and thicken.
Carve and serve with the sauce.
Use any leftovers for sandwiches with a dollop of your favourite chutney.