Pre heat the oven to 180C fan, or 200C in a conventional.
Heat a large, heavy based frying pan over a medium high heat. Add the oil or beef dripping and when it’s nice and hot, season the beef well with salt and pepper and carefully lay it down into the pan. Fry the beef on all sides until it is lovely and golden and smells divine.
Add the butter to the pan which will begin to bubble away furiously. Add the fresh thyme sprigs along with the garlic. Use a spoon to baste the beef all over with the herby, garlicy butter. Spend a few minutes doing this, it’ll really carry the flavour of the thyme and garlic onto the beef.
Transfer the beef and all the garlic and thyme to a medium sized roasting tin and place it in the preheated oven. Cook the beef, basting once or twice for 45 minutes – 1 hour or until the beef has an internal temperature of 50 – 55C for medium rare or 60C if you like it cooked for a little longer. Remove the beef, cover loosely and allow it to rest somewhere warm for 15 to 20 minutes.
To make a simple, yet delicious gravy, lift the beef out of the tray to a large plate or board. Set the tray over a low heat. Sprinkle in 2 tablespoons of plain flour and stir well, cooking gently for 1 - 2 minutes. Crush the garlic with the back of a spoon and scrape at any dark sticky patches on the bottom of the tin. Add the red wine along with beef stock. Bring the gravy to the simmer, stirring regularly until the gravy begins to thicken nicely. Pass the gravy through a fine sieve into a clean saucepan, pressing all the flavour out of the garlic with the back of the spoon or ladle as you go. Set the pan over a low heat and add 2 teaspoons of red wine vinegar and 1 tablespoon of cumberland sauce, stir well and season to taste with plenty of sea salt and pepper and stir well.