History
The Priory of the Holy Trinity was founded in 1229 by Gilbert d'Aquila. The original buildings consisted of a cruciform church with a cloister to the south, the chapter house on the east side of the cloister, the kitchen and refectory to the south and dormitories (over the cellars) to the west.

In 1388 the threat of French raids led Prior Leem to surround the Priory and its immediate grounds with a moat and build a gatehouse. The Priory was dissolved in 1537 and the church and the east cloister range were immediately pulled down for their building materials.

John Foote purchased the Priory in 1556 and transformed the south and west cloister ranges into a house. In 1587 the Priory was acquired by Herbert Pelham, an ironworker and landowner. He replaced Foote's work with a new stone wing but ran out of money and was forced to sell the property in 1599. The Priory was purchased by Thomas Sackville, later 1st Earl of Dorset, and the Sackville family owned the freehold for the next 300 years.

The Sackvilles let the Priory to a succession of tenant farmers and barns and farm buildings were gradually built around the house. In the late 19th century a corn mill was added to the site but the house itself fell into a decline.

In 1896 the Priory was bought by James Eglington Gwynne who set about restoring the medieval buildings. After 1924 the well-known conservationist architect Walter Godfry carried out further restoration and in 1959 the Priory was given to the Sussex Archaeological Society. The Society has continued the renovation and the corn mill is now in full working order.

Phenomena
Reported paranormal activity at the Priory includes a servant girl wandering the corridors and a monk has been spotted accompanied by the scent of incense. A young girl dressed in a tattered dress has been seen, while strange lights have been captured in the Priest hole.

Music emanating from a phantom harpsichord has been heard, shadows have been seen moving throughout the building and doors have been seen opening by themselves.

Investigation
This pilot episode of Most Haunted was a taste of things to come, providing a variety of activity. During Derek's initial inspection, a door appears to open of its own accord, as he connects with the energies a young girl, who is scared by the spirit of one Thomas Sackville. When Yvette is pinched by something unseen, Derek suggests this is the girl, Molly, trying to get her attention.

During the night vigils, Karl is startled by the appearance of the lower half of a man, his legs and long cloak, materialising by the fireplace. Light anomalies are the picked up in the same place. Later, in the stairwell where the spirit of Molly hides, one of the crew is tripped and Yvette claims to hear laughter at the same moment. More strange lights are filmed in the empty room.