Instructions

1. Preheat the oven to 200°C (Fan 180°C / Gas 6).
2. Peel and finely grate the fresh horseradish into a bowl. Add the Dijon mustard, lemon juice, olive oil, rosemary, thyme, and a good pinch of salt and pepper. Mix to form a thick paste.
3. Pat the beef dry with kitchen paper. Rub it lightly with olive oil and season well with salt and pepper.
4. Heat a large frying pan over high heat. Sear the beef on all sides until nicely browned. This should take about 8–10 minutes in total.
5. Transfer the beef to a roasting tray and leave it to cool slightly. Brush the horseradish and herb paste generously all over the meat.
6. Place the halved onion and garlic bulb in the tray alongside the beef.
7. Roast for about 45 minutes for medium-rare. If using a thermometer, the internal temperature should reach around 55°C (130°F). Adjust the cooking time depending on how you like your beef cooked.
8. Remove the beef from the oven and rest it on a plate, loosely covered with foil, for at least 15 minutes. This allows the juices to settle and keeps the meat tender.
9. Use the cooking juices in the tray to make a simple jus or gravy, if you like.
10. Carve the beef into slices and serve with your chosen sides and the pan juices.