Preheat the oven to 175 ° C (top / bottom heat). In a coated saucepan with a matching lid, heat the olive oil over medium heat. Roast the sliced onions, celery, carrots, bay leaves and sage for about 10 minutes, stirring occasionally.
Add the cubes of beef and dust with flour, stir. Add the Guinness, chopped tomatoes, brown sugar, salt and pepper. Stir and bring to the boil once.
Transfer to an ovenproof container with a lid and place in the oven for about 3 hours (or until the meat is done). If the stew is too runny afterwards, continue cooking without the lid until the desired consistency is achieved. Remove the bay leaves and season with salt and pepper.