Place the beef, flour, and seasoning into a plastic bag and shake. Meanwhile, heat the oil or dripping in a large heavy-bottomed pan. Fry the beef shin in batches until browned all over and set aside. In the same pan, adding a little more oil necessary, sauté the onions, carrots, and celery until soft for about ten minutes.
Add the tomato puree and leftover flour and cook out for another minute, stirring continuously, before adding the red wine and beef stock.
Add the beef shin back to the pan, stir everything together and place the marrow bones and bouquet garni, tied with string, on top.
Reduce the heat and place a tight-fitting lid on the pan. Bring to the boil and reduce the heat to achieve a gentle simmer. Allow to cook for about two hours then remove the lid and allow the sauce to reduce for another hour.
When the beef is cooked, remove from the heat and thoroughly cool. When cool remove the bones and the bouquet garni.
To serve, pre-heat your oven to 350 F / 180 C / Gas mark 4 and on a floured surface, roll out the half of the pastry to fit an oven-proof pie dish.
Carefully place the pastry into the greased dish and add the beef shin filling. Brush the edges with egg wash and top with remaining rolled out pastry, crimp the edges and brush the top with the rest of the beaten egg.
You can decorate with any pastry offcuts if you want. Place the pie in the oven for thirty to forty-five minutes until the pastry is golden and cooked.
Allow to stand for 5 minutes after baking and serve with horseradish mash and buttered peas.