Put the baco and oil in a frying pan and cook over a medium heat for a couple of minutes.
Add the birds to the pan and cook them for a few minutes on each side to brown the breasts. Put the birds and bacon into a large oven proof casserole dish.
Add the onion to the frying pan and cook for a couple of minutes. Add the garlic and celery and cook for a further 2-3 minutes. Pour in the tomatoes, puree, stock, worcester sauce and sugar. Bring to the boil, season well and spoon into the casserole.
Cover the casserole and put in the oven for 45 minutes.
Remove the lid, baste the pheasants, re-cover and cook for a further 15-25 minutes until the meat is tender.
Remove from the heat and leave to rest for 10 minutes before serving.