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Brisket needs a long, long soak (up to a week) in a vinegar and/or wine based marinade to break down that otherwise tough connective tissue.  Try wine or cider vinegar, olive oil, bay leaves, juniper berries, a bit of salt and black pepper and thyme, rosemary or whatever your taste is in herbs.  Turn it every day, keep it covered in the fridge and roast it slowly it next Thursday.

beef brisket cooked in a slow cooker is delicous and is easy to prepare...just brown the meat first in some olive oil then place in the cooker...using the same pan, fry some sliced onions and garlic till soft then add a little tomato puree (paste), some tinned tomatoes (just a few) , a large glass of red wine, some beef stock and some rosemary and thyme(season with salt and black pepper).....heat the mixture till it boils , then pour over the meat (you don't want the joint to be swimming in sauce, about half way up is ample)... add some whole, peeled potatoes to the pot then cook on the lowest setting for at least 8 hours.

Brisket needs a very slow long braise to break down and not be tough.  4-5 hours was just the beginning of your roast.

We do an overnight roast.  I marinade in wine for a few hours, then chop up onions and garlics in to the roasting pan, cover with foil and put it in the oven at 140-150C before I go to bed.  The next morning you take it out and let it rest.  When it comes to room temperature wrap it up and place in the fridge.  When you're ready to serve heat it up again and it will be moist and juicy.

Beef brisket can be seasoned with a sweet-savory sauce, wrapped in cooking paper then foil wrapped, and roasted until tender, which will take upto 3 hrs then served with sauteed mushrooms and pearl onions."