Built by the great architect Robert Adam between 1771 and 1778 for Lord Apsley, the Lord Chancellor, Apsley House stands alone at Hyde Park Corner and is also known as Number One, London. It is a Grade I listed building.

Today the house is run by English Heritage and is open to the public as a museum and an art gallery. However, the 8th Duke of Wellington still uses part of the building as a part-time residence.

Visitors can enjoy the rooms of Apsley House exactly as they would have been furnished and decorated in the late 18th and early 19th centuries. The house features the 1st Duke's art collection, porcelain, silver and furniture as well as Antonia Canova's marble statue of Napoleon. The arts collection includes over 200 works, including pieces by Landseer, Wilkie, Maes, Steen, Brueghel, van Dyck, Rubens, Vernet, Goya, and Velázquez.

The house was sold to the Duke of Wellington in 1817 as a London base to pursue his career in politics, and it has been owned and occupied by the Dukes of Wellington ever since. From 1818 to 1819 the architect Benjamin Wyatt was employed to carry out renovations. Wyatt added two bays westward to the original five, added the Waterloo Gallery (named after the site of the Duke's famous 1815 victory over Napoleon) to house the Duke's artworks and added a facade of golden-coloured Bath stone over the original red brick frontage.

The house acquired its nickname as Number One, London due to its position as the first house passed by visitors travelling into town from the countryside after the toll gates at Knightsbridge. It was originally part of a line of houses on Picadilly, which were demolished in order to widen Park Lane.

Rumour has it that during World War II King George and Queen Elizabeth heard that the treasures of Apsley House had not been evacuated and hence arrived personally in a van to remove the works for safekeeping.

In 1947 the 7th Duke of Wellington gave the house and most of its contents to the nation. It was also enshrined in law, however, that the family has the right to retain residence in just over half of the original house "so long as there is a Duke of Wellington." The family apartments are on the north side of the house.