Earlier Houses: There was a 17th century house on the site that was demolished to make way for the current house.

Built / Designed For: Sir Watkin Williams-Wynn, 4th Bt.

House & Family History: The 4th Baronet, a Welsh patriot who was involved in societies for the revival and promotion of Celtic traditions, cut a wide swath through 18th century British artistic society. Called the Welsh Maecenas and the Welsh Medici, Sir Watkin was one of the richest men in Britain and probably the greatest patron of the arts Wales has ever produced. He supported architects, musicians, artists, and the theater, in addition to being an avid collector of Old Master paintings. He hired Paul Sandy to accompany him on a sketching tour of north Wales, engaged Joshua Reynolds to paint portraits of his family, and commissioned fellow Welshman Richard Wilson to paint scenes of an idyllic rural Wales. No. 20 is a celebration of the Neoclassical design of Robert and James Adam, together with many of the finest craftsmen of the age. The Adam boys engaged Josiah Wedgwood (a friend of Sir Watkin, who was also an early patron of the potter) for a variety of work, Joseph Rose for the plasterwork, John Hinchcliff for marble chimneypieces, Domenico Bartoli for scagliola, and Antonio Zucchi, who painted the ceilings of the Great Drawing Room, the Music Room, and Sir Watkin's Dressing Room, in addition to ornamental door panels, bookcases, and overdoors. In 1936 Mewes & Davis linked Nos. 20 and 21 and added two stories to create a series of offices. This was all done for the Distillers Company, who purchased both houses in 1935. In 1940, during the Blitz, an oil bomb severely damaged the Adam Room at No. 20, which was later restored.

Collections: A painting of Sir Watkin and his mother by Joshua Reynolds, circa 1768-69 (see "Images" section), is today in the collection of Tate Britain. Richard Wilson's "Dinas Bran from Llangollen" (1770-71) is, together with a view of the valley by Wilson from the other direction, in the collection of the Yale Center for British Art, New Haven, Connecticut. Both paintings were commissioned from Wilson (a fellow Welshman) by the 4th Baronet, probably expressly for No. 20, which was also called Wynn House. In 1774 the 4th Baronet took delivery of a Neoclassical style chamber organ that he had commissioned for the Music Room of 20 St. James’s Square. The organ, whose case was designed by Robert Adam (who also designed 20 St. James’s Square itself) and made by the London cabinetmaker Robert Ansell (who also supplied mirrors and picture frames for Wynn House), was manufactured by John Snetzler in 1774. The organ's case features a central medallion with a profile of Handel, Sir Watkin's favorite composer, surrounded by two draped female figures: on the left Terpsichore, the muse of dancing and song, who holds a lyre, and, on the right, Euterpe, the muse of music, who has a musical pipe, or horn, in her hand. The two doors below open to reveal two keyboards. In the Music Room at Wynn House Sir Watkin hung two paintings on either side of the organ: "Orpheus" by Nathaniel Dance and "St. Cecilia" by Joshua Reynolds, which symbolized profane and sacred music. In 1863 the organ was reinstalled at the family’s Welsh country house, Wynnstay Hall, where it remained until it was purchased in 1995 by the National Museum Cardiff. The museum restored the organ and installed it in one of their galleries, where it can be heard as part of a program of regular public concerts.

House Listed: Grade I

Park Listed: No Park

Past Seat / Home of: SEATED AT EARLIER HOUSE: Allen Bathurst, 1st Earl Bathurst, until 1771. SEATED AT CURRENT HOUSE: Sir Watkin Williams-Wynn, 4th Bt., 1775-89; Williams-Wynn family here until 1906.

Current Ownership Type: Corporation

Primary Current Ownership Use: Offices

Ownership Details: Owned by Pembroke Real Estate of Boston, Massachusetts, and let as offices.

House Open to Public: No

Historic Houses Member: No