Season the oxtail well with salt and pepper, and then lay it out on a tray. Using a sieve, sprinkle half the flour over the meat, then turn it around and sprinkle the other half of the flour.
Heat a good splash of olive oil in a large non-stick pan and sauté the meat on both sides until browned. Do this in two or more batches, wiping down the pan in between if necessary. Set the browned meat and all the juices aside..
Wipe the pan and then heat another glug of olive oil in the frying pan and add the celery, onions, carrots, and star anise. Sauté until softened – about 5 minutes. Add the garlic & anchovies and fry for a further minute or so, then the tomato paste and cook for a few seconds.
Transfer the vegetables to the bowl of a pressure cooker or a large cast-iron lidded casserole dish.
Then into the dish goes the tin of tomatoes, red wine, red wine vinegar, sugar, and Worcestershire sauce and cook until the sauce has reduced by about half.
Add the chopped rosemary, orange zest, and beef stock. Nestle the meat back in, along with any juices.
If you are using a pressure cooker, ensure that the liquid does not fill above the maximum line. Cook on high for 50 minutes on high and then use a natural pressure release.
If you are cooking this in the oven, cook for 4 1/2 - 5 hours at 170C and until it is meltingly tender and falling off the bones.
Serve with mash or gnocchi and any vegetables that you love.