Cut the beef into 2 cm chunks and trim any excess fat and silverskin. Do not throw away the trimmings. Season the beef with salt and pepper, then toss with the flour until coated.

Add the trimmings to a large pot on medium-high heat. Let the fat render off, then discard the trimmings. Add the beef to the pot and sear for 3 to 5 minutes until evenly browned. Remove the beef to a plate.

Add the carrots, celery, mushrooms, and onion to the pot and let cook about 5 minutes, stirring occasionally. Add the garlic and cook another 2 minutes. Pour in the ale and scrape the bottom of the pot with a wooden spoon. Let simmer for 5 minutes.

Return the beef and any juices to the pot. Add the thyme sprigs, stock, Worcestershire sauce, a good pinch of salt and several grinds of freshly cracked black pepper. Bring to a simmer. Turn the heat down to low and cover. Let cook for 1 1/2 hours.

Fish out the thyme sprigs and add the potatoes. Simmer uncovered for 1 hour or until the beef and potatoes are tender. Add extra salt and pepper to taste. Serve with a small sprinkle of fresh thyme.