Open the oysters with a small, sharp knife. Place them in their shells on a grill pan. Do not overcrowd the grill pan – it is best to cook the oysters in batches. Mix together the bacon, garlic and parsley and season with pepper. Divide between the oysters, sprinkling over the top, then place under the grill and cook for 3-4 minutes until the oysters are bubbling and the bacon is sizzling.