Remove the meat from the fridge about an hour prior to cooking. Remove any packaging.
Place the oven on its highest setting (220°C fan, Gas mark 8) and allow to come up to full temperature. Drizzle a small amount of oil onto the meat and using your hands rub this all over. Season with a little flakey sea salt. Place the meat into a large roasting tray and blast for about 10-15 minutes until golden all over.
At this stage turn the oven right down to 140°C fan, Gas mark 3, add a little water to the bottom of the roasting tray and cook for about 15 mins/500g plus 20 mins for rare, 20 mins/500g plus 20 mins for medium and 25-30 mins/500g plus 25 mins for well done or until the internal temperature reads:
48c-50c for rare
53c-55c for medium rare
58-60c for medium
65-70c for well done
Cover loosely with foil and leave somewhere warm to rest for about 30 minutes.
Make a little gravy to accompany using the meat juices, by tipping away most of the fat. Stir in the flour and cook for 1 minute, then gradually stir in the wine and boil until reduced by half. Add the stock and also any meat juices from the meat. Simmer until reduced and a good consistency.
When ready to serve, slice into thin slices, serve on warmed plates with accompanying roast potatoes and seasonal vegetables, as well as generous smears of Colman’s mustard.