1 Pat the meat dry with kitchen paper.
2 Put the meat into a deep dish and put the onions, carrots, celeriac and bay leaves around it. Pour the red wine and white wine vinegar over the meat. Cover and put into the refrigerator for 2 days. Turn the meat over from time to time.
3 Make a cut in each chestnut on the round side and cook in salted water for about 10 minutes. Then drain, rinse in a sieve under cold water and remove the shells.
4 Quickly rinse the rosemary and pick off the leaves. Peel and halve the garlic. Preheat the oven to 150°C (130° fan) | 300F | gas 2.
5 Take the meat out of the marinade. Heat some olive oil in a pan and brown the meat over a fairly high heat. Transfer the meat to a roasting tin.
6 Strain the marinade through a sieve. Add 150 ml of the marinade to the roasting tin and arrange the chestnuts around the meat with the garlic and rosemary.
7 Roast the meat on the lowest shelf of the oven for about 1 ½ hours, basting with the rest of the marinade from time to time.
8 When done, take out of the oven, cover loosely with aluminium foil and leave to rest for about 10 minutes.
9 Season the sauce to taste and slice the meat thinly. Serve the roast wild boar with the chestnuts and the sauce. Serve with roast potatoes if you wish.