Spread the fat surface of the beef with a mixture of mustard and black pepper, then add some peeled shallots or onion halves around the joint to give extra flavour and colour to the gravy.
Set oven to 200℃/400℉/Gas 6. Place the joint in the hot oven for 15 minutes, reduce the temperature to 180℃/350℉/Gas 4 and allow 15 minutes per ½ kg for rare, plus 20 minutes extra for medium or 30 minutes extra for well done. To be absolutely accurate, you can use a meat roasting thermometer.
When the meat is cooked remove from the oven, cover loosely with foil and allow to rest for 30 minutes. This resting time allows the juices to settle; the meat firms up so it is easier to carve.
Spoon off the fat and add some wine or water to the juices. Boil over a high heat and taste for seasoning. Serve with the sliced roast beef, crispy roast potatoes, roast vegetables (or a creamy vegetable purèe to ring the changes).