Season the Beef and place on a rack in an oven roasting pan.
Drizzle oil over the Beef, then roast in a preheated oven at 160°C for 15 - 20 minutes per 500 g, plus an additional 15 minutes for rare, or 20 - 25 minutes per 500 g, plus an additional 20 minutes for medium-done.
For the basing sauce, mix all the ingredients together and start basting the Beef after the first hour of roasting. Keep a close watch on the roast to make sure the marmalade baste does not burn.
When done, remove the roast from the pan and place on a serving platter. Leave in a warm place for about 10 minutes before carving.