Rub the beef with the duck fat or goose fat (you can use beef dripping or olive oil if you can't get the fat), then liberally apply salt and and freshly-ground black pepper all over.
Place a heavy-based roasting tray on the hob on high heat and, when hot, add the beef. Sear the meat quickly on all sides to colour and crisp the outside (5-10 minutes).
Transfer the beef immediately to a preheated very hot oven (Mk 9 - 475ºF - 240ºC) for 20 minutes, then reduce the heat to moderately hot (Mk 5 - 375ºF - 190ºC) and roast for 30 minutes per kilo (rare), or 40 minutes per kilo (medium rare), or 50 minutes per kilo (medium), or 1 hour per kilo (well done). [15 minutes per pound (rare), or 20 minutes per pound (medium rare), or 25 minutes per pound (medium), or 30 minutes per pound (well done).]
Remove the beef from the oven, transfer it to a carving board and cover with foil to retain the heat. Allow it to rest in a warm place for 15-20 minutes. Serve with Yorkshire Pudding, lots of fresh vegetables and Port and Stilton Gravy.