This is the field where modern English history began. Here the Saxon king Harold Godwinson faced an invading Norman army led by William the Bastard. The Saxons held the high ground, fighting on foot; the Normans attacked with archers and cavalry. It was- as the Duke of Wellington said of Waterloo- a near-run thing. In the end the Normans won because they were trickier. The battle is most commonly known as the battle of Hastings- even though the town of Hastings is many miles away. Alternative names for it are Senlac or Santlache. William- now William I, King of England- had the Benedictines build an Abbey on the ground where the Saxons had stood. Maybe that laid the ghosts. The town that grew up around his Abbey is called Battle.
The Abbey was dissolved by Henry VIII and sold into secular ownership. The church and cloister and many other buildings were pulled down. What's left is divided in ownership between English Heritage and a private school.