Syon House, with its 200-acre (80 hectare/800,000 m²) park, is situated in west London, England. It belongs to the Duke of Northumberland and is now his family's London residence. The family's traditional central London residence was Northumberland House.

Syon House derives its name from Syon Abbey, a medieval monastery of the Bridgettine Order, founded in 1415 on a nearby site by King Henry V. The Abbey moved to the site now occupied by Syon House in 1431. In 1539, the abbey was closed by royal agents during the Dissolution of the Monasteries, and the monastic community was expelled. In 1541 and part of the following year, Henry VIII's fifth wife, Catherine Howard, was brought to Syon for her long imprisonment. In February 1542, she was taken to the Tower of London and executed on charges of adultery. In the late 17th century, Syon was in the possession of Charles Seymour, 6th Duke of Somerset, through his wife, Elizabeth Seymour ( née Percy). After the future Queen Anne had a disagreement with her sister, Mary II (wife of William III, also known as William of Orange), over her friendship with Sarah Churchill, Countess of Marlborough, she was evicted from her court residence at the Palace of Whitehall and stayed at Syon with her close friends, the Somersets, in 1692. Anne gave birth to a stillborn child there. Shortly after the birth, Mary came to visit her, again demanding that Anne dismiss the Countess of Marlborough, and stormed out again when Anne flatly refused. In the 18th century, Hugh Percy, 1st Duke of Northumberland, commissioned architect and interior designer Robert Adam and landscape designer Lancelot "Capability" Brown to redesign the house and estate. Work began on the interior reconstruction project in 1762. Five large rooms on the west, south and east sides of the House, were completed before work ceased in 1769. A central rotunda, which Adams had intended for the interior courtyard space, was not implemented, due to cost.

Syon Park
Syon Park borders the Thames, looking across the river to Kew Gardens, and near its banks is a tidal meadow flooded twice a day by the river. It contains more than 200 species of rare trees. Although the park and lake were designed by Capability Brown in 1760, their character today is nineteenth century. The circular pool has a copy of Giambologna's Mercury. The Great Conservatory in the gardens, designed by Charles Fowler in 1828 and completed in 1830, was the first conservatory to be built from metal and glass on a large scale. The conservatory was shown in a dream sequence in Meera Syal's 1993 film Bhaji on the Beach . It was also the setting for the music video to The Cure's 1984 single " The Caterpillar", directed by Tim Pope. Henry Percy, 11th Duke of Northumberland, who was head of the family from 1988 to 1995, was noted for planting many trees in the grounds of Syon. In 2002, the English poet Geoffrey Hill released a booklength poem, "The Orchards of Syon", to much acclaim. "The Orchards of Syon", focuses on the history of the region and in particular on the orchard of rare trees first planted in Syon Abbey. Robert Altman's 2001 film Gosford Park was partly filmed at Syon House. The London Butterfly House was based in the grounds of Syon Park until its closure on 28 October 2007 due to the Duke of Northumberland's plans to build a hotel complex on the land. In 2004, planning permission was granted for the deluxe £35-million Radisson Edwardian Hotel but was never actually built. Work on a Hilton Hotel started in December 2008 and is expected to open mid-2010. In November 2010, the results from an archaeological dig made two years before on the site of the new hotel were reported, with the excavations uncovering the remains of a Roman village that existed in what was then the rural outskirts of Londinium. Artifacts uncovered included 11,500 pottery fragments, 100 coins, and pieces of jewellery. Some of finds remain unexplained, such as the discovery of skeletons "buried in ditches placed on their side". Although the skeletons date from the Roman period, this burial practice was said by the senior archaeologist to be "more suggestive of unknown prehistoric rites than Roman practice". Syon House was one of the wealthiest nunneries in the country and a local legend recalls that the monks of Shean had a Ley tunnel running to the nunnery at Syon.