A Cistercian abbey was founded in Medmenham in the 12th century under the ownership of Woburn Abbey, though it was not officially recognised by royal charter until 1200. In 1547, at the Dissolution of the Monasteries, the abbey was seized and given to the Moore family and then sold privately to the Duffields. It was while in the possession of the Duffields that the abbey became infamous as the location of The Hellfire Club, formerly called the Monks of Medmenham.
In 1755, when Sir Francis Dashwood acquired the ruins of the ancient abbey from the Duffield family, he and John Montagu, 4th Earl of Sandwich attended a service at St. Peter's parish church in Medmenham where Sandwich released a small monkey in the church. The congregation fled in horror, sure that Satan himself had invaded their place of worship.
Today the abbey is a private residence and is not open to the public.
Above text taken from the Wikipedia entry for Medmenham.