Founded in 1077 under the sponsorship of William de Warrenne, one of William the Conqueror's trusted lieutenants, on the site of a former Saxon church dedicated to St Pancras. The boundary of the Priory followed modern day ham Lane to the east, Cockshut Road to the west, the stream known as The Cockshut to the south - most likely straightened during the construction of the Priory with a small wharf that ran into the grounds, and what is now Southover High Street, Priory Street and Mountfield Road to the north. The priory was well endowed with lands and rich enough to begin construction of a huge church which was completed by the 13th century and was said to be larger than Chichester Cathedral. During that century the priory briefly became the headquarters of Henry III's army prior to the battle of Lewes.
At dissolution only 23 monks remained and the priory had become unpopular with locals most likely aiding the strident protestantism that emerged within the town which indirectly led to its current bonfire celebrations. Having been suppressed in 1537 it was pulled down the following year with land been granted to Thomas Cromwell who built a house on part of the site that survived until that too was demolished in 1668. Much of the complex was reduced to rubble and for many years during the 16th century it became a large building material yard with much of the stonework carted off to be used in the local buildings of the towns as well as in manors such as Kingston and Hangleton near Brighton. The site was split in two by the construction of the Lewes-Brighton railway in 1846 though that work did unearth the caskets of the original founder and his wife. Since then the land north of the railway has remained in private hands will that to the south is now a public park.
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