In London's high-end Mayfair neighborhood, the Brutalist United States embassy, originally designed by Eero Saarinen, has been keeping watch over Grosvenor Square for 55 years. Diplomats will soon be exiting the building, however, as developers prepare for a hotel conversion by David Chipperfield Architects. The Architects Journal reports that Chipperfield bested Foster+Partners and U.S. firm Kohn Pedersen Fox Associates (KPF) for the job. However, there is some uncertainty as to whether Chipperfield has actually been commissioned or not. A spokesman for Qatari Diar, the company that now owns the site, refused to confirm that Chipperfield won the competition, stating: "A range of options on the best use of this important site are currently being considered." Qatari Diar Real Estate Investment has secured the remaining 939 years on the Mayfair district building’s lease and will not be allowed to alter the embassy's design as it was awarded grade 2 listing status for its historical and architectural significance and its "dynamic facade" in 2009. According to the Department of Culture, Media & Sport (DCMS), the concrete building was the "first purpose-built US embassy in Europe." The building's "dynamic facades, well-detailed stonework and consistency of detail and the innovative application of the exposed concrete diagrid" led to its protected status, the DCMS added. Occupying 225,000 square feet, the embassy takes up the entire west side of Grosvenor Square and currently has, according to Bloomberg, around 750 staff. Philadelphia-based KieranTimberlake has drawn up plans for the new U.S. embassy in Nine Elms, just south of the Thames, which is set to welcome occupants in 2017. The firm's winning design has been described by the Times as having a "moat" due to its semi-circular pond on one side. The new embassy resembles a crystalline cube and is surrounded by extensive public green spaces.