library book was discovered at Houghton in the mid-1950s, and returned 288 years late. Present day The house, including the north and south attachments, was designated as Grade I listed in 1953. Houghton has remained largely untouched, having remained "unimproved" despite the Victorian passion for remodelling and redecorating, due to the fact that for most of the 19th century the family lived mainly at Cholmondeley Castle in Cheshire, and only stayed at Houghton for the shooting. Houghton still belongs to the current Marquess of Cholmondeley, and parts of the structure and grounds are opened to the public throughout the year. Art Houghton once contained part of Sir Robert Walpole's great picture collection, which his grandson the 3rd Earl sold in 1779 to Catherine the Great of Russia to pay off some of the estate's accumulated debt. Included in the current collection of paintings is Thomas Gainsborough's oil painting of his own family, Thomas Gainsborough, with His Wife and Elder Daughter, Mary (circa 1751–1752). Walpole's collection of marble Roman busts was also considerable. In the early 1990s, Hans Holbein's "Lady With a Squirrel and a Starling" (1528) was removed from the walls of Houghton where it had hung since 1780. It was put up for auction to raise money to pay inheritance taxes and for maintenance of the house and grounds; and eventually, negotiations led to the painting's sale to the National Gallery for £17-million tax free because of special incentives in England for selling works of art that are considered national treasures. In the 21st century, art market inflation has placed enormous temptations in the way of the old families with substantial collections. In recent years, ownership of several pieces have been transferred in lieu of tax from the Cholmondeleys to the Victoria and Albert Museum. A major sale of items of pictures, furniture, silver and from Houghton estimated at $23 million was held at Christie's in London on 8 December 1994, with the intention of establishing an endowment fund for the future preservation of the building. Some artwork, such as William Hogarth's portrait of the Cholmondeley family is unlikely to be let go, and it remains on view at Houghton; but the Marquess admits that he is very aware that risk of theft is neither negligible nor negotiable. Jean-Baptiste Oudry's White Duck, stolen from the Cholmondeley collection in 1990, is still missing. Parkland and gardens Charles Bridgeman's landscaping plan