Woodchester Mansion sits on a much earlier Georgian country house called Spring Park. We do not know when work began on the new home, but by 1866, the clock tower was complete, and the roof was in place. Workers mysteriously laid down their tools in early 1868 and never returned. Rumours that several mysterious deaths and one murder unsettled them have never been substantiated but refuse to go away. After failing to complete the project, it was destined to become a mental institution. Still, the Second World War came, and Woodchester Mansion became a base for American and Canadian troops. During training, several lives were lost when a bridge collapsed, plunging some of the forces into the lake and to a watery grave. Their bodies were stored inside the building, and some believe that they haunt Woodchester's mansion to this day.
The original manor house for Woodchester in South West Gloucestershire was in the heart of the settlement of Woodchester itself, next to the old church. After a succession of owners, the manor was granted to George Huntley in 1564. The expense of creating a vast deer park is thought to have nearly bankrupted the Huntleys, and the estate and park were sold to Sir Robert Ducie in 1631. Later generations of the Ducie family decided to build a grand country house and, at the same time, create a magnificent landscaped park out of the deer park. Entirely why this site was chosen will forever remain an unknown fact. The valley’s steep sides mean that the sun is obscured for much of the year.
The Mansion house being positioned halfway down the valley’s length reduces the dramatic views that would have been seen if it had been built on a higher spot. The site is neither convenient nor easy to transport. It is thought that because it was not the Ducie's principal residence, they may have looked at it more as an isolated retreat. They decided to extend and adapt the hunting lodge and lay out a formal garden, and although a precise start date is unknown, Spring Park was constructed during the 1740s. Indeed, by 1750, it was finished, as Frederick, Prince of Wales, stayed, and in 1788, George III visited.

Before the visit of George III and only 30 years after the formal gardens were established, a start was made on extensively re-landscaping the grounds from plans drawn up by John Speyers, working with Capability Brown. This plan removed the more formal aspect of the garden to create a natural park.
William Leigh was born in Liverpool and educated at Oxford and Eton. At the purchase, he lived at Little Aston Hall in Staffordshire, where he had recently converted to Roman Catholicism. This and the Gothic Revival style in architecture were very fashionable and formed the ideology for the new house. He approached Augustus Pugin to draw up the new plans. However, in 1846, he became ill, and the project was dropped. Leigh meanwhile gave land in South Woodchester to a community of Roman Catholic Passionist fathers for a monastery and church. He then turned to Charles Francis Hansom, whose brother designed the famous Hansom cab of Victorian London, to take over and administer the architectural planning.

In 1857, Leigh got rid of Hansom and unexpectedly hired Benjamin Bucknall, a young man who was an aspiring architect and assistant to Hansom but needed to be more experienced. Bucknall set about studying Gothic Revival architecture. The result, Woodchester Mansion, is Bucknall's masterpiece. Woodchester Mansion was constructed from 1858 to 1870; in 1873 when William Leigh died, all work stopped abruptly, and the mansion was left more or less as it appears today.
In 1938, William Leigh's granddaughters, Blanche and Beatrice, sold the house and what was left of the estate to a mental health charity, the Barnwood House Trust. They intended to convert the mansion into a mental hospital, but subsequently, this plan was shelved. During the Second World War, the grounds were used as a billet for Canadian and American troops, and St Paul's Teacher Training College used the mansion. It was then abandoned to the elements. Fortunately, its isolated position meant it did not suffer from vandalism; it was not redeveloped.