Isle Delitable
Sir Palomides avenges the death of King Hermance in the Red City. According to Malory, The Delectable Isle is an island off the east coast of England.
Spurn Head peninsula, at the mouth of the Humber River, between Lincolnshire and East Riding, Yorkshire, satisfies Malory’s description. (If Glastonbury can be considered an island, so should a peninsula.)
Sources
Prose Tristan | 1230-1240
Le Morte Darthur | Sir Thomas Malory, 1469-1470