Begin by placing the bones in a meat roasting tin, tucking the chunks of carrot, quartered onion and celery in amongst them.Now, without adding any fat, just pop the roasting tin on to a high shelf in the oven and leave it there for 45 minutes, basting with the juices now and then. After that, both the bones and the vegetables will have turned brown at the edges. Now transfer them all to the very largest cooking pot you own, add enough cold water just to cover everything - about 4-5 pints (2.25-2.8 litres) - and add the rest of the ingredients, then as soon as it reaches boiling point remove the scum and lower the heat.Put the lid on but not completely (leave a little gap for the steam to escape, thereby reducing and concentrating the stock). Now simmer very gently for about 4 hours. When the stock is ready, strain it in to a clean pan, leave it to become quite cold, then remove the congealed fat from the surface. The stock is now ready to use, or for freezing for later use.