1. First marinate the venison: place the venison pieces in a large glass bowl and mix in the olive oil, salt and pepper. Melt the jelly with the vinegar in a small saucepan (or in the microwave) until dissolved. Pour over the meat, then mix through the remaining marinade ingredients. Cover and place in the fridge over night or up to three days. Stir through occasionally.
2. When ready to cook, drain the meat in a colander, reserving the marinade. Discard the solids that pass through.
3. Heat the olive oil in a large flame proof casserole and fry the bacon until just brown; remove and set aside.
4. Fry the onion slices, carrot and celery until they begin to colour; remove and set aside with the bacon.
5. Now fry the venison, in batches, until brown, using a little more oil if necessary. Remove the meat to a large bowl as it is browned. Sprinkle with the seasoned flour and toss through to mix well.
6. Preheat the oven to 170C/325F/gas mark 3. Pour the reserved marinade into the casserole and bring to the boil, scraping up any brown bits on the bottom. Skim off any scum that rises to the top. Add the stock and bring back to the boil.
7. Return the meat, vegetables and bacon to the casserole and add the bouquet garni and mushrooms. Bake in the oven for 2?2? hours or until tender. Check the level of liquid and add water if necessary.
This is fantastic served with mashed potatoes. It keeps well in the fridge for several days, or in the freezer.