In 1440 a Sussex Knight by the name of Roger Fiennes petitioned the Crown for the right to crenellate or fortify his manor of Herstmonceux. He had risen to prominence after serving Henry V at the Battle of Agincourt (1415) and later serving as Treasurer of the Household of Henry VI. He had amassed a considerable fortune and had decided to use it to construct a castle befitting of his family’s new found importance. The building was at the time the largest private home in England, and since it adopted the French fashion of building in brick, the castle of Herstmonceux was unique. The Fiennes family fortunes continued to rise until the reign of Henry VIII (1509-1548). From the 1520s the family appears to have been at odds with King Henry, and when the castle’s owner, young Thomas Lord Dacre, was implicated in the murder of a neighbor’s games keeper Henry VIII saw his opportunity. Thomas Dacre was executed at Tyburn in 1541 and the estate was seized by the crown. Fortunately, the family was reinstated to their estates in 1558 when Elizabeth I became queen and the family again prospered.
Seventeenth century England was rife with uncertainty and social unrest, yet the owners of Herstmonceux appear to have prospered, carrying out renovations and even were able to avoid the extremes of the 1640s when civil war gripped the country. During the Restoration (1660-1685) a significant amount of money was spent refurbishing the castle; new fireplaces were installed, elaborate oak carvings by Grinling Gibbons were added, and in the lady’s bower a large bay window was installed overlooking the moat to allow Lady Dacre, a daughter of King Charles II, to enjoy the view. Unfortunately, it was here that the family’s fortunes came to an end. The cost of renovations, and the excessive gambling and merriment of Lord Dacre at the restoration court bankrupt the family and in 1708 they were forced to sell the estate to Mr. George Naylor for £38,000. In 1777 an assessment of the castle was undertaken by the architect Mr. Samuel Wyatt, who pronounced the castle to be in such a poor state of repair that it was not worth saving. The furniture was sold off, the wood paneling removed, and the interior walls torn down. The bricks were carted away to be used to create a more modern mansion known as Herstmonceux Place on the northwest corner of the estate. In just a few short years the castle was reduced to little more than an ivy-covered gothic curiosity.
Advances in transportation and the growth of tourism in the nineteenth century turned Herstmonceux Castle into a popular tourist attraction for those holidaying on the south coast in nearby Eastbourne and Brighton. Tourists visited the castle to stroll through the gardens, climb amongst the ruins and enjoy a cup of tea in the tea gardens run by the Winchester family. However, the castle continued to deteriorate and by the turn of the century was in a very ruinous state and in need of attention. This would come in 1910 when an eccentric MP, Colonel Claude Lowther, purchased the estate with a view to restoring the castle to its’ former glory and creating a grand country home. Extensive restorations were undertaken and the southern half of the castle transformed. In 1933 Sir Paul Latham purchased the castle and continued the process of reconstruction, completing the remodeling of the northern half of the castle. Extensive work was also undertaken on the gardens and grounds, with the addition of a tennis court, a swimming pool, extensive plantings and the excavation and flooding of the moat. Further changes to the castle came during WWII when it for a brief time housed the Hearts of Oak insurance company which needed a place where its’ records would be safe from Germany’s Blitz on London. While Herstmonceux Castle did not see any serious action, it still felt the effects of the war and was on numerous occasions strafed by German planes. An RAF camp, part of RAF Wartling, was established on the estate and a large air-raid shelter was constructed immediately south-west of the drawbridge.
In 1946 Sir Paul Latham sold Herstmonceux Castle to the Admiralty, which established it as the new home of the Royal Greenwich Observatory. From the early 1950s until 1989 Herstmonceux Castle remained a centre of scientific research and home to one of the world’s leading astronomical organizations. However, “light pollution” from the nearby city of Eastbourne, along with other factors, combined to make staying at Herstmonceux impractical and in 1989 the RGO was moved to Cambridge. The castle was sold to developers who planned to turn it into a hotel and golf resort. The idea was opposed by a group of local residents who formed The Society for the Protection of Herstmonceux Castle. After a lengthy battle the castle and estate were saved from the developers.
By the end of the 12th Century, the family at the manor house at Herste had considerable status. Written accounts mention a lady called Idonea de Herste, who married a Norman nobleman named Ingelram de Monceux. Around this time, the manor began to be called the 'Herste of the Monceux', a name that eventually became Herstmonceux (pronounced Herst-mon-soo).