Preheat your oven to gas 7, 220C, fan 200°C Make a paste with a beef stock cube and 1 tbsp oil. Rub this into the beef. Heat a thick-based frying pan on the hob and add the beef, fat-side down. Once the fat has rendered and turned golden brown, turn the beef to sear all sides. Remove the beef from the pan and place in a roasting tin.
Return the pan (with the beef fat) to the heat. Add the leeks and cook until golden, then add the leeks to the roasting pan alongside the beef joint. Repeat this for the parsnips and carrots. Add the shallots straight to the roasting tin. Put the celery and sage in with the beef. Drizzle the fat from the pan over the joint and vegetables, and put the roasting tin on the hob for a few minutes to heat. For rare meat, transfer the joint to the oven and cook for 30-45 minutes (depending on your oven), turning the meat at the halfway stage.
Remove the joint and vegetables from the roasting tin and place on a board or large plate to rest.
Place the roasting tin on the hob and crumble a beef stock cube into the tin, adding a little water to deglaze. Mix thoroughly and transfer to a saucepan. Bring this to the boil and add a couple of drops of olive oil to thicken, and add texture to the gravy. Reduce the sauce to thicken and pour over the beef joint and vegetables.