Remove the beef from the fridge 1 hour before cooking. Preheat the oven 220C/200C fan/Gas Mark 7. Place the beef in a roasting tin on top of the shallots and season. Mix the horseradish and mustard together and spread over the beef. Mix the breadcrumbs and thyme leaves together and sprinkle over the top of the horseradish and mustard mix. Drizzle with olive oil. Place the beef in the oven and roast for 20 minutes. Reduce the heat to 160C/140C fan/Gas Mark 3. Roast for a further 20 minutes per 500g for medium beef, or when a probe thermometer reaches 60C in the thickest part of the joint. Or 15 minutes per 500g for rare beef, or when a probe thermometer reaches 50C-55C in the thickest part of the joint. Loosely cover with foil if the top starts to brown too quickly.
To make the Yorkshire puddings, sift the flour and salt in to a bowl. Stir in half the milk. Beat in the eggs and season with pepper. Beat until smooth. Whisk in the remaining milk and oil. Cover and chill in the fridge for 30 minutes before cooking.
Remove the beef from the oven. Place on a warm serving dish with the shallots, cover and allow to rest. Turn the oven back up to oven 220C/200C fan/Gas Mark 7. For the Yorkshire puddings use a 12-hole tin. Place 1tsp of sunflower oil in each compartment and heat in the oven for 3-5 minutes or until hot. Fill ¾ full. Place in the oven and bake for 15-20 minutes or until risen and golden. Remove from the tin and keep warm. Repeat with the remaining batter.
To make the gravy, pour off all but 1 tbsp. of fat from the roasting tin. Place the tin on a medium heat add the flour and stir for 1 min. Slowly add the stock and/or vegetable water and wine. Bring to the boil, reduce the heat and simmer for 2 minutes or until thickened. Season to taste. Just before serving pour in the juices from the rested meat. Pour in to a warmed gravy jug. Serve the beef with the Yorkshire puddings and gravy.