A new hotel building with five storeys and two basements was opened at the same site on 5 September 1874, designed by the English architect Edward Augustus Gruning. The foundation stone was laid by the daughter of the Belgian Vice-Counsul. The new building had a long curved façade facing the River Thames, close to Sion College and near the site of the new City of London School building that opened in 1883. The exterior was in an Anglicised form of the Second Empire Style, faced by white Suffolk bricks and Portland stone, with a Mansard roof covered with green slates and hips, ridges and dormers in zinc. An archway led to an internal courtyard, at the centre of which was a glass dome covering a billiard room below, later used as a lounge. The interior was decorated in opulent French style, with 230 guest rooms and many function rooms, including a dining hall 110 by 40 feet (34 m × 12 m) with space for 400 people. Furniture was imported from Paris.
A second wing opened in 1882, when the hotel became the largest in London, accommodating up to 480 guests, with a second dining room for another 250 people, and rooms for 150 staff.
Sir Polydore de Keyser had no children. His hotel was sold to a limited company in 1897, and a nephew Polydor Welchand de Keyser took over the management.
