The Longwitton dragon used to haunt the surroundings of Longwitton in Northumberland (UK).
Close to the town of Longwitton there was a wood containing three wells famed for their healing powers. One day a local man went to the wells to collect some of the healing water but instead found a large dragon lapping from the wells with a long black tongue. The dragon suddenly disappeared but the man could still sense its presence nearby. From that day on, the dragon would let nobody approach the wells. Then one day a young knight in search of adventure heard of the dragon and rode into Longwitton intent on killing the beast.
Before setting off to do battle with the dragon, the young knight rubbed a magical ointment onto his eyes which would allow him to see the invisible. He charged into the woods and fought with the dragon all day. However the many wounds he inflicted on the beast seemed to heal almost instantly. Exhausted the knight returned to the village ashamed of his failure.
He rode out the next day determined to finish the dragon off, but the same thing happened again and the knight was forced to retire once more. On the third day the knight decided to change tactics. He attacked less frequently and watched the dragon's movements closely. Noticing that the dragon always kept its tail on the surface of the wells' water the knight decided that the best course of action was to lure it away from the wells.
He dismounted from his horse and feigned defeat. The dragon sensed victory and rushed forward to finish him off. The knight, however, jumped back on his horse and rode past the dragon, blocking its path to the healing wells. The dragon was furious and attacked more ferociously than before, but the brave knight inflicted several mortal wounds and the dragon eventually succumbed to blood loss. With the dragon defeated, the wells returned to their former glory and the people of Longwitton rejoiced.
In Thomas Percy's Reliques, the knight is the Earl of Warwick, Sir Guy.