Dust the beef in seasoned flour, shaking off the excess. Heat the oil in a large casserole dish over medium-high heat and brown the beef in batches until golden. Remove and set aside.
In the same dish, add the onions, carrots, parsnips, and celery. Cook for 5–6 minutes until softened and lightly golden, then stir in the garlic and tomato purée, cooking for another minute.
Pour in the ale and bring to a simmer, scraping up any browned bits from the bottom of the pan. Add the beef back to the dish, along with the beef stock, thyme, bay leaves, and Worcestershire sauce.
Season with salt and pepper, then cover with a lid and simmer gently on the hob or in the oven at 160°C (140°C fan) for 2–2½ hours, until the beef is tender and the sauce rich and thick.
Remove the bay leaves, adjust seasoning if needed, and garnish with fresh parsley before serving.