Place the thyme, cayenne, paprika and garlic salt into a bowl and mix to combine. Spread a thin layer of the Dijon mustard all over the fat side of the beef joint. Sprinkle the spice mixture on top, patting it down gently to help it stick. If you have time, wrap loosely in cling film and allow the beef to marinade overnight.
Preheat the oven temperature to 200 degrees celsius. Pour the 3 tablespoons olive oil into a roasting tin/pan and allow to heat in the oven for 5 minutes. Add the onion, carrot and leek, bay leaf and fresh thyme, tossing to coat them in the oil. Season to taste and roast for 20 minutes until lightly caramelised.
Increase the oven temperature to 220 degrees celsius. Heat a large, heavy-based frying pan, adding the dripping or olive oil and, when the oil is hot, quickly sear the beef for about 30 seconds on each side – be careful as the spices will give off a strong aroma and make your eyes water! Transfer the beef to the roasting tin using the vegetables as a bed to sit on.
Add the red wine to the frying pan and allow to bubble down to burn off the alcohol, then pour into the roasting tin with half of the stock. Roast for 15 minutes until well sealed, then reduce the oven temperature to 200 degrees celsius once again and roast for another 40 minutes (for a 2.25 kg piece of meat).
As a general guide, after roasting the beef for the first 15 minutes, roast for an additional 10 minutes per 450g (1 lb) for rare; 12 minutes per 450 g for medium-rare; or 20-25 minutes per 450g for well done. Baste the roast with the red wine and stock every 10 minutes or so during cooking.
Remove the beef from the tin and place on a large dish. Allow to rest in a warm place for at least 10-15 minutes before carving.