Originally known as Forest Lodge, in the late 1760s Thomas Sandy was engaged by Lady Waldegrave to extend the existing house. It was subsequently described in a guide book, published in 1771, as "a noble edifice commanding a most extensive and delightful prospect of the Thames". No pictures seem to exist of the house before or after the alterations.
The next improvements, to the grounds, were the direct result of a Royal scandal. Lady Waldegrave had secretly married the Duke of Gloucester, brother of King George III, in September 1766. Gloucester's sympathy with his brother's recent banishment for another marriage-related decision meant that he admitted his marriage to the King in September 1772 and was also promptly banished from court.
As a former favourite, the Duke of Gloucester's banishment was particularly hard felt, so, to busy himself, he promptly set about improving his country house. Thomas Sandy was again commissioned, this time landscaping the grounds and adding plantations. In 1773 the Duke also bought the neighbouring house - The Hermitage - and renamed it Sophia Farm in honour of his daughter born that year. By 1776 debts had forced the family into self-imposed exile but the Duke was reconciled with his brother in 1778 leading to his restoration at court. Perhaps this return to favour spurred the Duke to seek to leave behind the estate he had spent so much time at during his banishment. The Duke and Duchess sold their St Leonard's estates in 1781/2 for the reputed sum of £10,000.
Gloucester Lodge, as it was still known as, was bought by the 3rd Earl Harcourt, in whose family the house remained until 1872. The house was then sold to Mr (later Sir) Frances Tress Barry who renamed the house St Leonard's Hill. He set about rebuilding it into it's final form (as shown in the Gallery). The alterations successfully created an elegant French chateau-style house. The main two-storey body of the house had three-storey towers on each corner - each tower having steeply pitched roofs with ornate dormer windows. The house had a largely rectangular footprint, slightly longer on the side leading out to the garden terraces. On that same side was also attached an extension with a similar roof.
The end for the house came following it's sale in 1924 following the death of Lady Barry. The new owner immediately set about demolishing the house, selling off anything possible. The shell and the estate were sold again in 1937 and the house was quietly left in peace to be overcome by nature. Even in the 1970s it said that approximately 40% of the shell remained though now all that's left are some minor ruins.
Description from 'Beautiful Britain - the Scenery and Splendours of the United Kingdom' published in 1894 by the Werner Company of Chicago:
"St. Leonards Hill, is situated in the parish of Clewer, Windsor Forest. It was formerly called Gloucester Lodge, it having become the property of the Duke of Gloucester when he married the original proprietress, the Countess of Waldegrave. At that time the building was enlarged and much improved, and, together with seventy-five acres of land principally laid out in pleasure-grounds and lawns, is said to have been valued at £10,000. In the beginning of the present century it was the property of General Harcourt, and now belongs to Mr. Barry. St. Leonards Hill is a name no doubt originating from the chapel of Saint Leonard of Loffeld in Windsor Forest, in connection with which there is still extant a document dating from the time of Edward III in which a large portion of the forest was granted to John the Hermit.
There are many beautiful features of Renaissance architecture in the building, which is finely situated and commands a splendid view. The ground belonging to it would seem at one time to have been a Roman encampment; for, particularly in the early part of the eighteenth century, numerous antiquities have been brought to light in course of building and other operations. Amongst these was a quaint old brazen lamp, unearthed from beneath a stone under which it had evidently been hidden, which was afterwards presented by Sir Henry Sloane to the Society of Antiquaries, and has since been chosen by them for their crest. Numerous coins also, dating from the times of the Emperor Vespasian and the Lower Empire, have been dug up from time to time on St. Leonards Hill, and purchased by the same society. Spear-heads, arrows, pieces of trumpets, various coins and weapons, pots and fragments of ancient earthenware, and other souvenirs, have since been found."