Peel and chop carrots, onion, garlic and celery.
In a small bowl combine flour with two teaspoons of sea salt and a teaspoon of cracked pepper and mix well.
Heat oil in a large heavy-based saucepan to high temperature.
Toss steak in flour mix to coat then sear in the hot oil for 1-1/2 minutes on each side. Remove beef from pan and turn heat down to medium.
Add garlic and vegetables then sauté for 10 minutes or until soft. Meanwhile, dice steak into 2cm cubes. Add tomato paste and thyme then sauté for a further minute.
Pour in passata and stock, then return beef to the pan along with the mustard, Worcestershire and thyme. Cover and simmer for 1 ½ hours stirring occasionally.
Remove lid and add the pearl barley and ½ a cup of water then simmer uncovered for 45 minutes. Season with salt and pepper and serve immediately.