Occupying a site at the northwest corner of the square, in the angle between Gloucester Place and Upper Berkeley Street, it was built for Mrs Elizabeth Montagu, a wealthy widow and patroness of the arts, to the design of the neoclassicist architect James Stuart.

Construction began in 1777 and the house was completed in 1781, whereupon it became Mrs Montagu’s London residence until her death on 25 August 1800. The house was destroyed by an incendiary bomb in the Blitz of London and the site is now occupied by the Radisson SAS Portman Hotel.

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Source: Wikipedia