Combine the flour, salt and pepper in a shallow dish, dredge the beef, shake off the excess flour and set aside.

Combine the beef broth, Worcestershire and mustard in a measuring cup and set aside.

Heat the olive oil in the pressure cooker over medium-high heat. Add the beef and cook, turning frequently, until lightly browned on all sides. Transfer the beef to a plate and discard any excess fat.

Reduce the heat to medium and add the olive oil to the cooker. Add the onion and cook until soft and translucent, about 4 to 5 minutes. Add the garlic and cook 1 minute longer. Stir in the beef broth mixture and tomatoes, scraping up any browned bits from the bottom of the pan. Return the beef to the cooker and bring the mixture to a simmer, raising the heat if necessary.

Cover the cooker, lock the lid into place and bring it to high pressure. Cook for 20 minutes at high pressure, then remove from the heat, release the pressure, taste the gravy and adjust the seasoning as needed.

Add the potatoes, carrots, turnip and thyme leaves. Cover the cooker and lock the lid in place. Bring the cooker back to high pressure, then cook the stew for an additional 5 minutes.

Remove the cooker from the heat and allow the pressure to drop naturally before opening. Spoon the stew into bowls and serve immediately.