Rub the fillet with 1 tablespoon olive oil, then sprinkle over the thyme and season with salt and pepper. Heat a heavy-based frying pan. Add the fillet and cook for 3-4 minutes, turning frequently to ensure an even searing that gives the meat a browned crust. Remove from the pan and leave to rest for 3 minutes. Meanwhile, combine the tomatoes and rocket in a large bowl. Add the remaining olive oil and the lemon juice. Season to taste. Toss gently together, then spread the rocket and tomatoes on a large plate. Thinly slice the beef and arrange on top of the rocket and tomatoes. Drizzle the balsamic vinegar over the beef and add a grinding of black pepper. Finish with the Parmesan shavings.