The herbs are what might have been used in Anglo-Saxon East Anglia, but use whatever you might fancy. Try to use fresh, although dried is acceptable. Put one sprig or generous shake of rosemary down the middle of each fish. Chop all the other herbs and seasonings and mash them into the soft butter. Use this to coat the fish generously on each side. Griddle, barbeque or grill it for 4-5 minutes on each side or till the skin is well browned and the flesh flaking off the bone. Baste now and then with the butter which runs off. Serve at once with lot of fresh bread and a salad or a simple green vegetable.