Cut the beef into 5cm (2 inch) pieces and pat them dry before seasoning with salt and black pepper.
Warm the olive oil in a heavy pot over high heat, then brown the beef pieces well on all sides in batches. Set aside browned meat.
Lower the heat to medium and add more oil if the pot seems dry.
Sauté the minced garlic and chopped onions for about 3 minutes until they begin to soften, then add the diced bacon.
Cook until the bacon is nicely browned, then add the chopped carrots and celery, stirring to combine.
Sprinkle the flour over the vegetables and stir continuously for 1 minute to cook off the raw flour taste.
Pour in the Guinness beer, chicken stock, and tomato paste, stirring well to dissolve the flour and blend the sauce.
Add the bay leaves and thyme sprigs, return the browned beef and any juices back to the pot, ensuring the liquid just covers the ingredients.
Cover the pot, reduce the heat to a gentle simmer, and cook for 2 hours until the beef is tender.
Remove the lid and simmer uncovered for an additional 30 to 45 minutes until the beef easily breaks apart and the sauce thickens.
Skim excess fat from the surface if you wish, then taste and adjust salt and pepper as needed.
Take out the bay leaves and thyme sprigs before serving.
Enjoy the stew alongside creamy mashed potatoes for a delicious comforting meal.