Public access to the historic War Office in central London has been made a condition of the planning permission granted for the development of the Grade II-listed, Edwardian property into a 125-bedroom luxury hotel.
Westminster City Council has approved the plans by the owners of the 1,000 room building, global investment company Hinduja Group and Spanish-based OHL Developments, to redevelop the property, with the stipulation that its historic character is not lost.
The building, located at the junction of Horse Guards Avenue and Whitehall, will be transformed into a luxury hotel following the construction of a double-height basement to provide space for a spa and leisure facilities as well as three additional floors. Due to open in 2020, the hotel will include extensive restaurant, bar and meeting facilities, as well as a ballroom.
The proposals will also involve the creation of 88 flats and a £10m donation to Westminster's affordable housing fund.
Richard Beddoe, senior chairman of planning, Westminster City Council, described the plans as and "exciting development" which will bring "another iconic hotel" to London.
"These plans give this building a new purpose while respecting its place in history. The War Office has played a pivotal role in our country's past and ensuring members of the public had opportunity to visit and experience this iconic building first hand was a key consideration in our decision."
The building was acquired last year on a 250-year lease by the Hinduja Group and OHL Developments for £350m. An operator is yet to be announced for the hotel, although Raffle Hotels & Resorts has been reported as being the "preferred" option.
The decision to allow the conversion of the War Office is the latest involving the transformation of a former government building into a hotel as part of a wider sell-off of unused office space in a bid to raise more than £1b for the nation's coffers.
Planning permission was granted in 2013 to Prime Investors Capital to develop a luxury hotel within Admiralty Arch, which the company had acquired a 99-year lease on for £60m. However, the building is yet to be transformed into a hotel.
In 2011, the 294-bedroom Corinthia hotel opened in a building between Northumberland Avenue and Whitehall Place once occupied by the Ministry of Defence.
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